You generally are 1 or 2 cm taller early in the morning as during sleep the pressure from gravity on your spine is reduced.
In all seriousness, he might have permanently compressed his spine >1" just by doing those heavy calf raises.
There's gotta be a list of recommendations somewhere, "how not to lose 6" of height in the gym": NO heavy standing calf raises, do them seated or on a 45°/horizontal leg press machine only! NO heavy squats, do leg presses or smith machine squats where you lean against the bar! (Dorian did not shrink.) Take caution when doing heavy shrugs and farmers walks, decompress your spine afterwards.
