There's two major errors in your theory. One, the problem with the K-frames was the hot 125-grain SJHPs--these weren't around for most of the 25 years of the Model 19//66's existence. Hence, no problem. Second (which compounds the first), LE became smart and begin practicing/qualifying with the issued carry rounds instead of target wadcutters. The combination of the two factors--shooting a round for which is was not designed to handle and shooting it a lot lead to problems with the .357 Magnum K-frames for the heavy users.As a magnum, the K frame was in production approximately 25 years before the intro of the L frame. If there was a real problem it would have been noted and dealt with before then.
There's two major errors in your theory. One, the problem with the K-frames was the hot 125-grain SJHPs--these weren't around for most of the 25 years of the Model 19//66's existence. Hence, no problem. Second (which compounds the first), LE became smart and begin practicing/qualifying with the issued carry rounds instead of target wadcutters. The combination of the two factors--shooting a round for which is was not designed to handle and shooting it a lot lead to problems with the .357 Magnum K-frames for the heavy users.
I've always considered the L frames to be a marketing gimmick by S&W to sell more guns.
In 44 you're definately better off with a 3 inch 624 (6 shot) than the 3 inch 696 (5 shot) and probably why the 696 is no longer in production.