Just wanted to add:
It is exactly the same case for holding. As far as I remember the PANS OPS holding speed for a Cat B Turboprop was something like 175 knots, but it sepcifically says "for holdings limited to Cat A & B only" or something like that. The important bit is the word "holdings" which means holding patterns. So you only need to fly the hold at that speed or less if it was designed for A & B only. Otherwise you could fly a regular published hold in your C150 at 220 knots and not break any rules (other than you AFM speed limits!) or bust any airspace or protected areas.
Of course it doesn't make sense to hold at 220 knots in an average turboprop but you could legally do it all the same.