I dont know the difference either I think its best if you like the sound of something and then decide what it means to you.
I consider myself doing p365 because I take a photo a day. That being said... I missed 3 whole weeks last year and simply documented how I was burnt out on it. That is life after all.
Plus I include mine in to weekly p52 style LOs that will have 7 photos and daily journaling, just a few sentences to tell what is going on, some days barely any journaling, others lots... depending on what we do
I am not in to the whole project life thing because I do not want to keep up with something I can not do digitally. If we want to keep "ephemera" that is what our memory boxes are for lol