If the person is producing quality new or rebuilt vintage bicycles that are then put into general circulation, I have no issue. I would agree with the frustration if someone were buying up large quantities of material or parts and hoarding them without putting to use. But if the result is a bicycle put into the market or circulation among users and collectors, then great.

If you look at whatever vintage bike you enjoy, the stock of these things is finite. Some are more limited in number than others, but scarcity still applies. Putting one more old bike back into circulation by fixing it up, including using up stocks of old parts if needed, is a positive, not a negative.