For the first time, I don't just get a feeling of "Meh" from Legends & Lore - Monte is absolutely and fundamentally wrong, IMO. From the top....
Actually, I've never heard this said about 1st or 2nd Edition, and barely ever about 4e.
I'm sorry, but, "I personally have never seen it or heard it and therefore the speaker is fundamentally wrong," is perhaps among the weakest arguments in existence.
It's only the spellcasters who continue to see big boosts in power, and while this leads to a "spellcasters rule!" mentality, they're rare enough that I haven't seen this translate into "the game breaks". (Although, maybe it should have.)
Referring to this as a "mentality" is as bad as Monte saying the breakdown is *only* if you look at the game in a certain way. You, like he, are dismissing the experience of others as being in their heads, rather than being in their experience, and well-considered.
As far as I am concerned, the disparity in general effectiveness between the pure spellcaster and others in 1e and 2e counts as "breakage". It is one of the most common complaints about the game, and for you to dismiss it as a mentality rather invalidates your "I have never heard this" support. You darned well have heard it, but you're actively dismissing it.
For someone claiming Monte's fundamentally wrong, your argument has too many fundamental similarities to his.