If he rented the property to someone who isn't paying his rent that's not a squatter issue and Florida's new law isn't about that. It's about someone illegally moving into someone else's property without permission and with no type of rental or lease agreement from the owner of the property.
Excellent point that the tenant not paying is different than a squatter. Although the outcome is probably the same for the landlord.
There was a guy in Portland, OR that found a lady camping on his property just down the hill and behind some trees in the home he lived in.
He told her to leave as she was trespassing. She cried and said she had all of her stuff here and she can’t just leave, and asked for a couple of days so she could move her stuff. The homeowner, being a nice guy, said yes.
Well, a few days passed and she had not moved anything or left. The guy called the police and he explained the situation. Turns out that because he didn’t kick her off right away and allowed her to stay - she wasn’t trespassing anymore. It turned into a “tenant” relationship so she had a month or more before she had to move, he had to provide legal notice, etc.