Here are my thoughts regarding piano technicians knowing how to play a piano, or not. If they can tune, they can play at least a little, and likely much better than they realize. I would also imagine there are, however, some piano technicians who can tune well, but perhaps can't play much of anything coherently, other than the intervals that they need to play in order to tune. They have to at least be able to play certain notes, and combinations of notes and intervals. Actually, playing the piano involves playing the right notes in specific combinations and intervals at the right time.
Also, there can be a tendency for someone who doesn't play the piano all that well to say they can't play when they can actually play a little at least (ask me how I know this...
). But it is possible for a piano tech to not be able to play the piano very well, yet, they may be excellent piano tuners/technicians.
Also, it has been my observation, since I've become interested in pianos, and been a member of Piano World, that, quite often, individuals who are/were formally trained classical pianists to become piano technicians, piano dealers, piano salespeople or piano teachers (full-time) because they may not earn enough income as a concert pianist to be a full-time concert pianists. Hence, they have to supplement their income in these other areas, whether part time or full time. I suppose not every highly trained and skilled concert pianist can earn enough money playing concerts or playing for money. I'm sure there are other jobs where pianists can earn enough money to make a living being full time pianists.
So, to recap, many piano technicians are/were also formally trained and skilled pianists (who also learned to be technicians); many piano dealers are/were formally trained and skilled pianists; and, of course, many piano teachers are/were formally trained and skilled classical pianists. These individuals may well supplement their income by performing, but their primary day jobs are working as technicians, dealers, salespeople or piano teachers; all of which are noble, respectable and rewarding occupations.
Again, this is just a personal observation and an opinion.