I'm on macOS 10.13.6 on a MacBook Pro (15-inch, 2018). I'm using BTT to show a shorter function-key bar (only F1-F6) next to the compact control strip. I also have haptic feedback turned on so the keypad clicks when a button is pressed or released, along with the usual button highlight.
I've noticed that sometimes I'll tap one of the F-key buttons, it will highlight briefly, but there's no haptic feedback and the F-key isn't issued. It looks like there's debouncing going on, which is good, but the highlighting seems to be done before the debouncing, not after.
The key shouldn't highlight unless the key has actually been recognized. (Yes, small issue, but I thought you'd want to know.)