The whole puking thing doesn't hold weight either imo.
I can do one set and make myself puke, doesn't mean I did anything good during the session though.
To this point though, I have thrown up A BUNCH training legs.....
I think what it all comes down to though, just like most everything, is to the individual.
MOST guys don't train NEARLY as hard as they think they do. Myself included. Until you train with someone who knows what real training is, you just don't know what you don't know though.
Something that I recommend to everyone, and I have my clients who are willing to do this is, record your top sets and watch them later in the day.... You'll see you left some in the tank 99% of the time. I see reps I leave behind all the time and I consider myself to train pretty hard but, during the set your mind wants you to stop and will fuck with you and make you think you're done when you really aren't.
If you're a high volume trainer, which most are, who trains extremely intense, which most DON'T, then yeah, training legs twice a week isn't going to work because you simply can't recover in time.
If you're a low volume, high intensity guy, yeah, twice a week can work and has for me if you throttle the volume back and manage recovery.
If you're a high volume guy who doesn't train with high intensity, your legs will probably suck.... Most guys