Very good point about the accessibility perspective regarding font size and contrast. I will also look into if the font should be replaced with a more readable one.
iPhone 15 Pro here and for me (old, eyesight finally starting to give up) they are a bit small and the contrast low - difficult to distinguish between the F and P in the middle channel of today's puzzle.
Could maybe do with the vertical bars being about 50% bigger and the letters scaled a bit more than that. Plus a high contrast option (white channels with black letters with white letters in the middle bit? Something like that anyway.)