I find that I often play too slow when first learning a piece -- talking about the guitar part here, which determines the tempo of a self-accompanied song -- but eventually start playing too fast after I have learned the mechanics of playing the desired notes/chords through many repetitions.

It seems to be more difficult to slow down after developing some facility at playing a song than it was to gain speed while learning.

It may be that, in making a deliberate effort to control tempo, a performer might wind up playing more slowly than originally intended. Maybe?

Perhaps it was pure accident that one person commented on songs she noticed as having been played slower than normal. On another night, another casual listener might have commented on one or two familiar songs being performed faster than expected. Unless, that is, more of your regulars there at Market Rasen belong to the slow-down school than to the speeder-uppers. You know that better than I...

;^)