Hi littleego,
Yes, you can turn it off. I have FN2 set to Focus Check (and had it this way for 3 generations of x-series.) You can cycle through the 4 choices, micro prism, split screen, peak highlights, and nothing.
When I shoot film using my Pentax Spotmatic, I never use the center split and instead focus using the any part of the screen by judging the sharpness of the image.
I've begun doing the same thing with my X-T5. For my purposes, Fujifilm has essentially killed manual focus aids - so I'm upping my game and going old school. I use focus check for the magnified view and focus "off the glass," no aids.
The old setup was better, but it seems Fujifilm is not concerned any longer with the usability of the products they make and sell - so carry on.