Using Sheldon's calulator with a 700x25 tire size:

@60RPM

52x11=22.3mph
52x12=20.4mph
52x13=18.8mph
53x11=22.7mph
53x12=20.8mph
53x13=19.2mph
54x11=23.1mph
54x12=21.2mph
54x13=19.6mph

@80RPM (what I consider the upper limit of "mashing")

52x11=29.7mph
52x12=27.2mph
52x13=25.1mph
53x11=30.3mph
53x12=27.7mph
53x13=25.6mph
54x11=30.8mph
54x12=28.3mph
54x13=26.1mph

Since I can't imagine anyone riding normally at 60rpm let's assume the person in question tends more towards the 80rpm side of things.

That's CAT1/pro peleton speed. Something's fishy.