Actually, he is mostly right. TR2 and early TR3 had only one replaceable cam bearing (the front one); the other cam journals ran directly against the block casting (same as TR6). Very early TR2s also had a weaker camshaft, that would sometimes break under racing conditions.
But I wouldn't say that "most" of them self-destructed. A few, no doubt, but many of them are still around today. And both problems are relatively easy to fix, so I'm guessing that most of them have been. To add the cam bearing inserts, you just line-bore the block, which is a well-understood machining process (if not particularly cheap). And the later, beefier camshaft is a drop-in.
Oddly enough, I was just reading the other day that some of the racers are breaking camshafts again, because the beefier section gets undercut when regrinding a stock cam for more valve lift. That was the reason I opted to have mine ground on a new blank, rather than a regrind.
PS, Piggott says the uprated camshaft started at TS1636E, while the bearing inserts started at TS8997E. So I may be mistaken about some early TR3 not having the inserts.