Well even the information contained in your post and the reply ("I am the founder of GNOME, and [something about his official connection to the project during the 2 -> 3 transition]; I can assert that nothing like what was described here happened: No patent lawsuit was threatened; fear of such lawsuit did not play into our decision to develop GNOME 3; and Ubuntu did not start Unity because they were rebuffed from GNOME 3") would be adding to the discussion.

As for "need", I think depends on what you mean. Is he morally obligated to set the record straight? No, of course not. Will his original reply, with only his username and no other information, convince very many people? Not really: if he actually wants to correct what he sees of as misinformation, he does "need" to do at least a little bit more.

FWIW I certainly don't remember "Avoid being sued over Windows 95 design patents" being part of the motivation for the 2 -> 3 transition being discussed in the wider community at the time. (As opposed, say, to the DCO -- aka "Signed-off-by" discipline -- adopted by the Linux kernel, which was definitely designed to defend against MS-funded SCO nonsense.) But it would certainly make me feel better about Linux desktop fragmentation if it were true.