I see all sorts of answers online, but am not fully convinced. I tried finding some research on the longevity of clothes between wash and wash + dry. Considering that it dries for hours just the mechanical movement should damage the clothes I would assume?
Also, “dries for hours” implies a less-heated condensation dryer. I’m used to the forced air heating kind. I believe the heat is a bigger source of damage than the actual friction action. Your armpits, legs, butt-against-seat, or sole-against-sock-against-shoe provide much more violent, repetitive, and focused friction than a dryer.
Granted, there can be a lot of lint that is removed in each cycle, which implies a lot of fabrics getting frayed. This is more common in things with loose, fluffy fiber like towels, blankets, or felts. Greater friction from greater surface area combined with less tight bindings and yarns leads to more fabric loss. But I haven’t seen a ton from generic pants and shirts loads.