Exactly, and at that time I was naive to put my (only first name) name on Google, as it is my only account. And they figured it out from their patients' records and sued me.

I've seen this several times in Google maps, the business owner finds out who the client is (gym, doctor, even ice cream shop) and confronts the client in the comments or even personally (seen once) instead of taking in the feedback

Defamation is when you say something you knew to be false.

Leaving a review that is honest is absolutely fine.

And when you get sued that's judge who has to decide that and for that you go to court, and for that you need a lawyer. Hence why most people just CBA...