I can't comment on the SNES30 Pro admittedly as I do not have one, but I do have the standard SN30 (both the older SNES30 model and the 2017 revision for the SuperNT) and both have contact design on the PCB that's inaccurate to the original. They just use four circular contacts in the cardinal directions, unlike the original, which had tabs (vertical for the contacts on the X axis, horizontal on the Y) that led to more accurate inputs and cut down on erroneous diagonals. The SN30's essentially got the same design quirk as the Switch Pro controller with inputs, in that the way the d-pad rocks and activates contacts will cause unintentional presses if slightly off-center. This is easily demonstrated by pressing the very end of a d-pad direction and rocking it back and forth a bit, while not intentionally putting pressure on any other direction. Whether or not people notice it or experience it is one thing, but it's commonly cited as a flaw by myself and others.
It is very noticeable on anything that needs diagonals a lot. Contra, Street Fighter, etc. A/B it with the real thing and it is just awful. Diagonals fire a lot when you want a straight-up down or up or whatever.
I did the tape mod with some Polyimide tape but I had to fiddle with it like 20 times to get it just right. It's at about 90% as good as the original now. And one of the 20 times I took it apart and put it back together, apparently one of the LEDs got broken, so I can't tell if it is connected now.
I don't understand how people don't notice it, honestly.
Word is that the 8bitdo mod kits are better, but I heard the SN30 was better than the NES30 also at first...and it isn't.
The Krikzz genesis controller is supposed to be amazing, though it had better be for the price.