The Merchant Center UCP integration hub is now gradually rolling out in the United States, offering merchants new capabilities. This update reflects a name change on the help page and a shift in rollout timing, with Australia and Canada following next year.
Merchants using this hub can now choose UCP capabilities such as cart transfer to merchant site, native checkout on Google, and identity linking. The previous FAQ regarding UCP-powered checkout for select US merchants was removed, aligning with these updates.

Read the official help page here: How to onboard to the UCP integration hub in Merchant Center.
This update was spotted by Hana Kobzová.