When i updated my system (F31 > F32), these repo’s were automatically activated.
Fedora 32 is still beta.
Pre releases have update testing repos enabled by default because… the whole system is still in test
When the final release comes out they will be disabled for you.
To answer your question, you can still disable updates-testing just fine, however if something is broken, you will not get the fix unless someone else tests it and it hits the stable repos. Therefore, I would recommend to leave them on, although the system could be a little wobbly, and wait until the Final release, when they get disabled automatically.