Exactly. Besides, it is called probable for a reason, otherwise they would have named it certain cause.

If the LEO honestly thinks he has a good reason, that's enough. It is up to you to demonstrate malice, ill intent and what not in court, in order to obtain compensation.

Example: somebody is shot and as the patrol car arrives they see you running away. Running in the street is perfectly legal and they didn't see you materially shooting, yet you'll be detained.
Once they find you have nothing to do with the shooting, you are set free, but you won't have any recourse for wrongful imprisonment, or anything like that.