TLDR; yes, TypeORM "supports" temporary tables
The problem lies in the code flow in your code. There is no guarantee about what happens to the temporary table between the requests.
Here's a quote from postgresql documentation:
If specified, the table is created as a temporary table. Temporary tables are automatically dropped at the end of a session, or optionally at the end of the current transaction (see ON COMMIT below).
You should do every you need with the temp table in a single transaction which guarantees you always use the same connexion.