The only explanation I’ve heard that makes sense is when it’s running a business out of the home and you have clients/customers coming and going. The increase in traffic is not accounted for in their insurance and blah blah. Extending that to WFH is either someone not understanding some landlord’s rights posts they read on some dark corner of the internet or, I don’t know, idiocy? Either way you’re signaling you’ll be a problem landlord.