The frame number problems that Kodak struggled with were particularly strange, because the effect that users had to deal with was that the ink pressed into the emulsion caused the emulsion to be sensitized, resulting in more density in that part of the negative image.
So one ended up with lighter toned numbers and letters in the skies and other parts of the image on the prints.
Film emulsions are designed to be very, very sensitive!
I understand that, but one might have thought that Kodak, with >125 years of roll film experience (1899 for 616), would have cracked this by now. Ilford have only had about 100 years!
We can see from Fujifilm's products, the issue can be solved, or least a much longer shelf life can be obtained for bold printed numbers before any "print-through" effect is visible (well past the normal expiry date). Fuji's 120 spools are also better designed than either Ilford's or Kodak's. I think at some point in history they put some R&D effort into the whole roll film packaging process, which is a little different than spooling 35mm cassettes.

