Catch up contributions at a previous employer with short limitation year

A previous employer (whom we acquired, but didn't take on their 401(k)) had a short limitation year, and, thus, a small 415(c) limit.  Accordingly, a few employees hit the 415(c) Limit and the previous employer reclassified some as "catch-up" (even though they hadn't hit their deferral limit) so they could max out on 415.

I don't think that affects us, but does anyone see any issues?

I'd say no, but obviously be sure you apply those catch-ups towards each participant's catch-up limit for the appropriate calendar year, including other catchups that may occur in the surrounding years.