But it's not though? Early generations, sure. But we're at the point now where dropping a folded phone really does not have much of a difference in chance of breaking in than dropping a regular candybar phone.
You're right in that technically it causes wear. In that regard, I suppose the fold mechanism would fail eventually. So it's not going to be your daily driver for the next 10 years. But no phone is. Modern folding phones absolutely do well for the normal life of a phone (4-5 years maybe??).
Ime, battery has been the first thing to shit the bed of any given phone (folding or not). Yes, you can get them replaced, but that's become either a complicated and/or expensive process nowadays. Your battery is going to become unusable before your screen breaks simply from wear alone.