I've also heard often that frequent stops/starts are not good for the miner HW in the long term. Mostly due to the temperature changes between operating and rest state, thermal dilatation can eventually damage the chips. If that's the case, it doesn't really matter if stopping is clean or just power-stop.
I don't have anything against this "theory", in fact, I do tend to believe that it makes a lot of sense, however, I have a few S9s that have been mining like a beast for about 4 years, those gears are turned off and on at least once a day, sometimes 3-4 times a day, and they are treated like shit, up to this point, zero issues. On the other hand, I had some S17 series gears treated very well, not much off/on, very good cooling setups, and they died in no time.
So really it all boils down to the quality of the miner, if the gear is already bad as is, I'd imagine that turning it off and on more often could speed up the failure process, but if the gear is rock solid, I highly doubt it will kill it before it becomes unprofitable to mine anyway.