Yes, to one own's needs, absolutely! For instance, she does say we can up our ptotein if we feel we need more; we can add 1 friendly carb right from the start if we want to keep working out normally or anyway more than recommended in P1; she also says you are free to keep drinking the cranwater in all phases and keep having two LLCs in all phases, although in P2 and 3 the regimen is slightly different (only 1 LLC in P3, cranwater in a 50-50 mix with water in P2 and P3). However, all those things don't change the plan itself, they mainly "borrow" certain items from another phase.

AnnLouise also says that anyone would benefit from drinking the lemon water and having 2 eggs daily; that's something that can be included in any way of eating, it's not exclusive of the FFP. She says you can implement as many of as few points of the FFP as you like in your diet, and you'll still see benefits.

Of course anyone can take anything from any plan and make it part of their eating habits, that's fine. But that doesn't mean they are on that plan. If someone just uses a principle of it or has a diet that is "inspired" by that plan but doesn't follow it closely, then they are just doing their own thing. Which is fine. It doesn't make them wrong, but it also doesn't make them authorities in how to follow the plan, because they are not following it themselves, really.

Bottom line: all plans have specific regimens. You are on Atkins if you follow the Atkins regimen as outlined in the book; you are on The South beach Diet if you follow it as outlined in the book; you are on the The Fat Flush Plan if you follow its regimen as outlined by the author. If you don't, then you are not on the plan. You are doing your own thing. Fine for you, but not necessarily what everyone else should be doing.