I saw this occur several times in the span of 20 minutes, so I can only presume it happens more than I care to imagine.
22R/04L is not a taxiway entrance to 31R. Its…well, it’s a runway. And as with every other airport, you don’t simply start taxiing down a runway you were not cleared to enter.
Here is a portion of the airport diagram (assume I remembered to properly label the runway with 04L):
If you wish to (and are allowed to) enter runway 31R for takeoff west of 22R/04L, you may do so via E or maybe even DB. East of 22R/04L, via Y. You do not enter 31R by entering 22R/04L without permission, just as you wouldn’t enter a different runway at any other airport.
Also, if you wish to cross 22R/04L, you do so via taxiways FB or YA (perhaps E, though unlikely). “Cross runway 22R” does not give you permission to enter 22R/04L, then backtaxi 31R. Doing so is entering, not one, but two runways without permission. Not a recipe for sticking around very long.
Here is how it appears in IF:
I’m not sure why this.particular runway would be seen as different from all others, but watching it happen several times in such a short span, I can only imagine it was not a fluke.