Personally I am of the belief that titles are for politics, something GM Angel Cabales frequently said, and that while ranks and titles can be disputed or taken away, one owns one's own knowledge and that is a gift which remains throughout life (to paraphrase folks like John Wong, Wally Jay, Richard Bustillo and other elders I've met in the arts).
Anthony Davis has always said that he was the first to publicly call Angel by the title of "grandmaster" and I've never heard anyone dispute that. However, here is a little story that I heard Angel tell on a few occasions to myself and others:
Back when Dan Inosanto and Richard Bustillo were setting up shop on their own in the late 1960's, they approached Angel and asked if he would be grandmaster of their organization. Angel told them (and was quite fierce in his retelling of this every time) that he was already a grandmaster, and if he let them, his own students, "make" him a grandmaster, then what would prevent them in the future from thinking they could "unmake" him as grandmaster. In other words, he declined from a position of authority. This is allegedly why Angel appears first in Guro Dan's original book, being his original FMA teacher, but Villabrille is named as a grandmaster, having accepted their offer of the title.
Not everyone may accept this history, but it is one Angel stuck with through the years I knew him. This is not necessarily inconsistent with GM Davis' telling, because this was something done in private, whereas Anthony Davis promoted Angel to the public in ways Angel would or could not do for himself.
As for anyone else's titles, that is an endless source of discussion and debate in the MA community at large. I know people who dispute Vincent Cabales' claim, and I know people who dispute Anthony Davis' claim. There are others within the Serrada family who have also created their own organizations, and within them they are the grandmaster as it is they who teach the teachers and dispense ranks. If we are to show respect within the Serrada community, it means we should acknowledge that the art has grown and spread, and not just under one umbrella. We don't have unity, we have community, and that is a way we can come together in peace.
The martial arts have plenty of charlatans (I'm not referring to anyone I've mentioned herein) who claim rank and skill beyond their due. Rank is like clothing, and not all wear it equally. There are folks I know who are quite humble but as worthy as anyone gracing the covers of magazines. I prefer to acknowledge each person for who they are, and what they have done in terms of personal growth and contributions to the art and society in general. The measure of a man is not found in the color of his belt or in a piece of paper, but what is in his heart and soul.
Just my own opinions ....