Nope.... most fit very easy. I put my thumb on in under 5 minutes, that included taking out the original pin on the bucket. I really thought I didn't put it on right because it was 'too easy'.
it looks like the plates were not welded on at the same spot / aligned properly. A simple solution would be to just drill out each side maybe a 1/16" larger. It is not really a frequent pivot point under stress. My factory thumb has a good bit of play at that mounting point.
If the tractor /BH is under warranty, I would have the dealer fix it or drill it out.... make sure you get paperwork from them showing what they did.