Is your WLAN vendor being straight with you?

I was talking recently with a former network IT professional, who had a lot of experience with large-scale wireless LANs. Now he's doing WLAN consulting with enterprise clients. Part of his focus (and another topic) is scaling WLANs for very high-density user locations. But in the course of that, he said something I found interesting, and disturbing. In trying to optimize the WLAN performance for the access points, he found that the WLAN vendors have little useful information and what they do have they're reluctant to share. He wants to know things like "what's the actual throughput of this access point" and "how many people can I get on it?" And yes, there are a lot of variables involved with answering those kinds of questions. And the variables can...well, vary. But this network professionals says that some vendors either don't have, or refuse to give him information about what their own tests have shown; or they only share information verbally; occasionally, they'll give him documents that aren't public. Reliable performance data seems basic in evaluating WLAN products and optimizing them in production WLANs. Vendors should WANT to give this information; and perhaps their refusal to do so should warrant them being excluded from consideration. Is anyone else running into this kind of reluctance? When you DO get information, is it valid and reliable?