It doesn't cause any problem, it just does the opposite of what it was meant to do/fix.
As i understood, that Menu bar fix for CX20751/2 was to fix the issue where if you connected the headphones (that had mic), when you clicked at the menu bar Volume icon while holding Option where it shows this:
View attachment 343183
When you connected the headphones/headset that had microphones, the menu bar didn't update accordingly and showed up like the picture above, while it should show this:
View attachment 343185
That fix was basically just a GUI/Graphical issue that the menu wasn't updating, as soon as you entered on Sound Preferences.. it updated/updates automatically (pretty much like the early battery meter issue we had on early High Sierra Development stages where lets say when you booted battery was 50%, it kept staying like that until you clicked on it, "not updating on real time").
So this issue is about the same, even with the patch active, to be honest it's still there sometimes, also sometimes it updates by itself after some minutes, but on macOS Mojave that issue has been fixed, when i remove that patch, the menu bar updates in real time, while if i leave the patch active, it doesn't update correctly (patch breaks it on macOS Mojave - returns same behavior).
Hopefully you understand the issue, as my english may not be perfect i tried to describe as best as i could.
So from macOS Mojave, feel free to remove that menu bar fix KextPatch for CX20751/2.