The testing is made with the right pressure from that level. The thing is that the test doesn't take what I would call "real life use" into account.
Hence, in the end, the client who isn't someone aware of all that, when he reads "30m", he concludes that he can swim with it. When you're told that it is ok for 30m you naturally think it is ok for swimming and even diving a little.
Which is not the case at all. This is what is misleading IMHO.
Cheers, Mark