Unfortunately, IME, the Venn diagram of gentle parenting and shit parenting doesn't so much overlap, but the two circles are essentially on top of each other. I think the problem is nearly every shit parent, incorrectly calls themselves a "gentle parent.". So the two things have been unfortunately become interchangeable to a lot of people.
My friendship group of mums (through school, say hello to or maybe have a brief coffee with etc, not close proper friends) I would say totals about 30. Of which 5 call themselves gentle parents. I have no idea how they actually parent their DC. But I do know their awfully behaved children are not welcome in my home, and most other mums avoid them for playdates/party invites. I also notice that the GP mother's think their DC are superior, mainly due to how superior they are as a mother, to a cringe worthy level.
I have a family member who gentle parents. One of her DC hasn't gone to school for over a year now. Never used to be a problem, but now it's a thing. He's simply realised he can get away with it. She doesn't like the word "No" and will accept zero constructive criticism or help, and can't see all she's doing is enabling him. Is she an actual GP? She says she is, but who knows?
So, to be clear, I (and I think a lot of people) don't really know what GP is. But all the people I know who claim to be practicing it, have awful children. And because I don't know what it is, or how it's different to what they are doing, and don't care enough or have the time to look up other people's parenting styles, I just accept them saying they are GP and see the evidence of that in how their DC behave.