Sure you're right, muscle moves weight, but for a natural guy to put on weight your body composition will change and you wont be lean anymore, I think we can agree on that. I know some guys can be 200lb+ and maintain low BF while natural, but I can't, I've been there, tried that, this weight is pretty high for me with my current bodyfat.
I already stated in the original post that I know progress is slow when you're not prepared to gain weight. I don't believe it's impossible, like I said I've seen guys below 10%bf lifting seriously heavy weights. And not guys whole bulk and cut either. I'm talking about guys who are lean (and natural) all year round. It's harder, but it's possible with years of training.
And aside form 1 error about westside (I forgot speed day, but they do alternate deadlift and squat, so ME is sometimes once per 2 weeks for squat), sure 531 has multiple templates, at LEAST one of them has once per week squatting. My point was that here's a bunch of different recommended frequency from popular programs, and that point stands despite your corrections, so to say it made no sense is a stretch to say the least.
I've never heard any disclaimer about what kind of people should be doing bulgarian method, other than you should not jump right into 4+ days per week. Since my previous program had squats 3 times per week I didn't see it as a huge shock to my body.