Cannot use Comparison Operator eq in Mongo Aggregation Spring because of Spel error Expected 'rsquare(])' but was 'comma(,)'

Question

I'm trying to replicate this stage in Java

{
  evaluaciones: {
    $map: {
      input: '$evaluaciones',
      as: 'eval',
      in: {
        porcentaje: '$$eval.porcentaje',
        detalles: {
          $map: {
            input: '$$eval.detalles',
            as: 'det',
            in: {
              porcentaje: '$$det.porcentaje',
              productoAcademico: {
                $first: {
                  $filter: {
                    input: '$prodAcads',
                    as: 'prod',
                    cond: {
                      $eq: ['$$prod._id', '$$det.productoAcademicoId']
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

By doing this

BsonDocument t = new BsonDocument().append("$map", new BsonDocument()
        .append("input", new BsonString("$evaluaciones"))
        .append("as", new BsonString("eval"))
        .append("in", new BsonDocument()
            .append("porcentaje", new BsonString("$$eval.porcentaje"))
            .append("detalles", new BsonDocument()
                .append("$map", new BsonDocument()
                    .append("input", new BsonString("$$eval.detalles"))
                    .append("as", new BsonString("det"))
                    .append("in", new BsonDocument()
                        .append("porcentaje", new BsonString("$$det.porcentaje"))
                        .append("productoAcademico", new BsonDocument()
                            .append("$first", new BsonDocument()
                                .append("$filter", new BsonDocument()
                                    .append("input", new BsonString("$prodAcads"))
                                    .append("cond", new BsonDocument()
                                        .append("$eq", new BsonArray(
                                            List.of(new BsonString("$$prod._id"),
                                                new BsonString("$$det.productoAcademicoId"))
                                            )
                                        )
                                    )
                                )
                            )
                        )
                    )
                )
            )
        )
    );

I also have used Aggregation API

VariableOperators.Map map = VariableOperators.Map
        .itemsOf("$evaluaciones")
        .as("eval")
        .andApply(eval -> eval.getMappedObject(new Document()
                .append("porcentaje", "$$eval.porcentajes")
                .append("detalles", VariableOperators.Map
                    .itemsOf("$$eval.detalles")
                    .as("det")
                    .andApply(det -> det.getMappedObject(new Document()
                            .append("porcentaje", "$$det.porcentaje")
                            .append("productoAcademico", new Document().append("$first",
                                    ArrayOperators
                                        .arrayOf("$prodAcads")
                                        .filter()
                                        .as("prod")
                                        .by(prod -> ComparisonOperators.Eq.
                                            valueOf("$$prod._id")
                                            .equalToValue("$$det.productoAcademicoId")
                                            .toDocument()
                                        )
                                )
                            )
                        )
                    )
                )
            )
        );

I use as a part of an "$addField" here

AddFieldsOperation formatResults = Aggregation
        .addFields()
        .addField("evaluaciones").withValueOfExpression(t.toJson()) // Applied here
        .addField("sistemaCalificacionId").withValue("$$REMOVE")
        .addField("sistemaCalificacion").withValueOfExpression("{$first: '$sistemaCalificacion'}")
        .build();

    TypedAggregation<Curso> cursoDatoTypedAggregation = Aggregation.newAggregation(
        Curso.class,
        match,
        sistemaCalificacion,
        prodAcads,
        formatResults // Here
    );

    return this.reactiveMongoTemplate
        .aggregate(cursoDatoTypedAggregation, CursoDato.class)
        .singleOrEmpty();

But in both cases I get this error

org.springframework.expression.spel.SpelParseException: Expression [{"$map": {"input": "$evaluaciones", "as": "eval", "in": {"porcentaje": "$$eval.porcentaje", "detalles": {"$map": {"input": "$$eval.detalles", "as": "det", "in": {"porcentaje": "$$det.porcentaje", "productoAcademico": {"$first": {"$filter": {"input": "$prodAcads", "cond": {"$eq": ["$$prod._id", "$$det.productoAcademicoId"]}}}}}}}}}}] @293: EL1043E: Unexpected token. Expected 'rsquare(])' but was 'comma(,)'

It seems that Spel doesn't accept Arrays. I tried to parse it as an object according to this but this didn't work. Is there any other way to replicate that stage?