Heat damages thc yes, but bear in mind joints burn approx 600 degrees C or above,

And your food would be completely ruined at 600 degrees C so it's fine.

THC vapourizes around 200 degrees tho so when people say make sure its well covered, follow their advice, usin something paste-like such as peanut butter would be good because its easier to accomplish a complete seal around the pot so it doesn't all go into getting your oven high

Jonny