My understanding is that yes, the strictness of the posting rules changed, AND they introduced the concept of trespassing even when it isn't posted at all. You get a lower penalty I believe, but you are still guilty.

For example. Unposted land, you run into the landowner and he asks you to leave and not come back. For all purposes, that land is now posted TO YOU. If you are caught on it you can be prosecuted. Yes there's the wiggle room you mentioned, but it's still off limits to you. It was done to balance land owner rights vs public access traditions.

Same for a single posted sign where you park your car. It's posted. However you could make the argument that you came in a different way and didn't know it was posted, that will work EXACTLY once.