Does he really say "They weren't armored on the underside"? Well, the Tiger has 20-26mm at the bottom, that's as much as the M4 has on top! How do you penetrate that with a ricochet (=deformation and loss of energy) at an extremely flat angle?
Allied fighter pilots did claim a lot of tank kills by rockets in France too. British command investigations found out that they were vastly exaggerated, with actually very few tanks really being killed by rockets. Just as an example how pilot claims and reality can differ ( I'll try to dig it up again.)
I know that the fighter drivers did try and 'bounce' the 50s underneath tanks having heard that from a Jug fighter bomber driver directly. Someone clearly planted the seed that it might work. Whether they did or not will always be in dispute
In terms of the rocket Tiffies. Clearly the message was sent, whether it was effective or not that the fighter bombers were doing the job. I think the other thing folks assume is that all the Tiffies were carrying rockets, when that was not the case. RCAF Tiffies in Normandy were only loaded out with bombs and they played a big part in Falaise. I would suspect that a 500 or 1000 pounder going off near a tank was much more effective then a rocket.
Ironically, at least to me, is that the folks who don't want to believe Michael Wittmann's Tiger was killed by Firefly, claim it was done in by a rocket Tiffie that day, although there were none over that battlefield. I guess it all depends on what message you want to send