Whether it is appropriate to store point in time data at the fact vs dimension (scd) table?

Question

I have following OLTP relationships:

User (userid, username)

Customer (customerid, userid, customername)

Sales (salesid, customerid, saledate, saleamt)

User has customers. Customer has sales.

In the DW I am loading the data as follows:

User (userid, username)

Customer (customerid, userid, customername)

Sales (salesid, customerid, saledate, saleamt, userid)

Note: user id is actually not on the fact table but I am adding it so as to hold who the point in time user was for the customer on that sale record.

Every night the ETL will do a SQL merge on sales table without changing the userid.

I am trying to understand whether this is an alternative to implementing slowly changing dimension at the customer table?