Events created using the Advanced Calendar API not showing up on Google Calendar Android app

Question

I'm adding all-day events to a calendar using the following code:

function main() {
  const response = JSON.parse(UrlFetchApp.fetch(API_URL).getContentText());
  const forecasts = response.daily;

  deleteEvents_();
  forecasts.forEach(e => {
    const forecast = new Forecast(e);
    console.log(JSON.stringify(forecast));
    console.log(forecast.getForecastText());
    Calendar.Events.insert(createEvent_(forecast.getForecastText(), forecast.date), CAL_ID);
  });
}

function createEvent_(summary, date) {
  const formattedDate = DateUtils.toYYYYMMDD(date, "-");
  return {
    summary: summary,
    start: {
      date: formattedDate
    },
    end: {
      date: formattedDate
    },
    transparency: "transparent"
  };
}

function deleteEvents_() {
  const today = new Date();
  const from = DateUtils.addDays(today, -1);
  const to = DateUtils.addDays(today, 7);
  console.log(`Retrieving events from ${from} to ${to}`);
  Calendar.Events.list(CAL_ID, {timeMin: from.toISOString(), timeMax: to.toISOString()}).items.forEach(event => {
    console.log(`Deleting: ${event.summary}`);
    Calendar.Events.remove(CAL_ID, event.id);
  })
}

I can see the events on the web version of Google Calendar but they don't show up on the app. I created another all-day event manually to test, and the one I created manually shows up on both the web version and the app. So next I got the properties of the manually-added event and one of the events I created via my script to see if there was any difference using Calendar.Events.list(CAL_ID, {timeMin: new Date("2022-04-30").toISOString(), timeMax: new Date("2022-05-01").toISOString()});.

Manually-created event:

{
  id: 'xxxxxxxx',
  creator: { email: '[email protected]' },
  end: { date: '2022-05-01' },
  created: '2022-05-01T00:49:18.000Z',
  etag: '"xxxxxxxx"',
  kind: 'calendar#event',
  organizer: {
     email: '[email protected]',
     displayName: 'weather',
     self: true },
  reminders: { useDefault: false },
  htmlLink: 'https://www.google.com/calendar/event?eid=xxxxxxxx',
  summary: 'test',
  transparency: 'transparent',
  updated: '2022-05-01T00:49:18.774Z',
  sequence: 0,
  start: { date: '2022-04-30' },
  iCalUID: '[email protected]',
  status: 'confirmed',
  eventType: 'default'
}

Script-created event:

{
  creator: { email: '[email protected]' },
  updated: '2022-05-01T00:28:26.176Z',
  htmlLink: 'https://www.google.com/calendar/event?eid=xxxxxxxx',
  created: '2022-05-01T00:28:26.000Z',
  sequence: 0,
  start: { date: '2022-05-01' },
  reminders: { useDefault: false },
  eventType: 'default',
  status: 'confirmed',
  etag: '"xxxxxxxx"',
  iCalUID: '[email protected]',
  end: { date: '2022-05-01' },
  organizer: { 
     self: true,
     email: '[email protected]',
     displayName: 'weather' },
  id: 'xxxxxxxx',
  summary: '🌧 (12.97℃-16.41℃)',
  transparency: 'transparent',
  kind: 'calendar#event'
}

Sorry for the difference in the order of the JSON contents, I copied and pasted the response Google Apps Script gave me (except that I redacted IDs for privacy). But I don't see anything that could result in one being displayed in the Google Calendar Android app and the other not. Am I missing something? What else can I check?