I do not know what the chances are of it not working, but it is not zero: we get a few requests per day on discord where the problem is the missing level-shifter. In many of those cases, the people got the instructions from youtubers who due to lack of knowledge did not mention that it is sometimes required to have a shifter. So if you make tutorials for others to follow, you should defintely add a levelshifter, you could still mention that it can work without it but not always.
edit:
see also my analysis here: Levelshifter Analysis