I have confirmed that this problem has been fixed (or at least no longer happens) with
mod-template-engine-1.7.1
and the tenant schema for mod-template-engine-1.7.1 is purged fro the DB

I tried to reproduce it on my local environment:

DB table for mod-template-engine before disabling module:

Sent request to disable mod-template engine:

After that DB doesn't contain the schema for mod-template-engine and for any related modules:

, could you please clarify if this flow is correct? It seems like it works as expected.

More information from :
I found these problems when testing the steps to delete a tenant.
tests failed because the tenant was not completely deleted from the database and left a mess that had to manually be cleaned up. That's fragile and one could easily delete the wrong thing.
I would give this a high priority because all modules are suppose to manage this detail and should not require going under the covers to get direct DB access.