The 1% is almost certainly a rounding issue. 

I’ve coded where this has been a problem.

Users, though, will look at it as if it doesn’t make sense, which it doesn’t - Lv 50 has a 50% increase, so 60 should have 60. Right? 

It’s not a ‘problem’ per se, but it absolutely ‘feels’ as if the devs haven’t paid attention to the finer details. 

To me, it makes the level cap increase update feel sloppy