Most logical analysis to date and thanks for pointing it out.
Of course, some of the sky priority customers may be one timers in F or C or elites on a partner. That would reduce the medallion count.
Analysis of a Gold as 50k may also be wrong as 10-20 K may be from Amex. That would increase the number of medallions, if each was only flying say 40k.
Assuming Plats were 1/3 of GM and DM 1/3 of PM, that would give a number of 35 DM, 100k PM and about 350k GMs, in line with previous speculations.