I have a similar issue; Cool zones I place outdoors in my desert base cool down the ground, but no buildings. So plants that are planted on the ground are fine and growing, but all my potted plats are dying. Same goes for other buildings, like columns and such. Only free space gets cooled down.

Edit: Though it seems the plants still think its too hot regardless, and refuses to grow. Note I do have plant growing in temperature zones enabled.

I believe the issue is objects that are placed on the tiles that are being temperature adjusted. If you place any object, such as a sleeping spot or a plant pot, then the proxy heat will no longer work for the tiles that the object is occupying. It wasn't like this before, so a recent update broke how proxy heat interacts with tiles that are already occupied by other objects. This will definitely need a fix, otherwise using proxy heat for anything other than planting zones becomes completely useless.

Edit: Someone made a mod patch to fix this issue. This should allow objects to not block temperature outside: https://steamcommunity.com/sharedfiles/filedetails/?id=3439148119&searchtext=ProxyHeat+

Oh my hero, thank you!