Although centrally located block such as lantern, bell, hanging sign no longer connected under fencegates, chains are still can be connected to fencegates.
What I expected to happen was...:
Chains should't be able to connected under fencegate
What actually happened was...:
Chains are able to connected under fencegate
Steps to Reproduce:
1. Launch Minecraft in 22w43a and place fence gate
2. try to place chain under the fence gate
3. you'll see the chain can be connected to fence gate in a floating state
Chains do not require a supporting block; they can float, so I'm almost certain that this is intentional.