If you query sys.databases, such as:
SELECT is_encrypted,name,user_access_desc FROM sys.databases WHERE database_id = 2 OR database_id = 7
It “might” throw you off. Would you not expect to see is_encrypted set to 1 for TempDB?
I thought I remembered earlier editions of SQL Server showing is_encrypted = 1 for tempdb, and I definitely remember 2016 showing 0 even when the database is encrypted.