There is a legal distinction that really matters on a daily basis. A renter who fails to pay rent isn't a squatter. A delinquent renter cannot be instantly arrested for trespass. Someone who enters without permission can be instantly arrested without much in the way of process (trespasser, robbers, drunk people etc). Someone who had previous permission can only be evicted after a lengthy process.

Where "adverse possession" aka squatter's rights exists, one much stay without the permission of the owner. A potential adverse possession can be avoided by the landowner giving permission. That stops any running clocks as the possession is no longer "adverse" to the rights of the owner.