As far as I remember, Find Next Formatting never used cmd-g as that has always been the Find Next shortcut (it’s a standard Mac system shortcut – try it in Safari and TextEdit).
The Find by Formatting equivalents were always on cmd-opt-ctl-F and cmd-opt-shift-G as they are now. Perhaps you changed the cmd-G shortcut at some point?
It was definitely like this in Scrivener 2, and I used this feature quite a bit (different find-next for the two search systems is very useful). I rebind the very clunky ⌥⇧⌘G to something a bit easier…
This hasn’t changed. The keyboard shortcut for this in Scrivener 3 is identical to the keyboard shortcut in Scrivener 2. As brookter says, only Find Next (for text) was bound to Cmd-G. They can’t both be bound to the same thing.