A good bet is to ask them..."Where are your students or people you have taught for more than just the recent year or two?" And see what they come up with.
That's actually a good question to look at from a number of angles, Dan. For instance, think how many good students (out of how many studied in the schools) people like Takeda, Ueshiba, Chen FaKe, Wang Hai Jun, or etc., etc., have or had. In Aikido, for instance, obviously Ueshiba had these skills and so did some of his students, to varying degrees, but look at how the knowledge of the skills was essentially lost down the line. That's a good entre' into the topic I've been suggesting that people "talk" a little more, even though talk is, as you say, cheap. Anyone can claim anything, but a knowledge of basics can't really be BS'ed to fool anyone with experience.
In a few years, I suspect that there'll be a lot more open discussions and a lot of today's claims will be looked back on humourously, so I'd suggest caution and a clinical approach.