Phone 2 user from the launch here. Nothing Phone LTPO doesn’t work like that (because it’s incapable of doing anything right). It works as follows
Drops to 1hz above 86% brightness; Drops to 10hz above 56% brightness; anything below 55% brightness refresh rate always stays at 120hz.
One more thing you’ll notice is, all haptics are stored under one settings. So you can’t even pick which you want on or off. Welcome to the most restricted android ever.