You didn’t quite get it either. Tremolo picking is the gateway into attempting to primarily use AP for string crossing.
My point was that early on, much emphasis is placed on tremolo picking (single string AP) and synchronizing it with the left hand. Furthermore, beginners start out playing patterns that are geometrically organized so that string crossing is easy. They don’t get trapped with pentatonics. Everything good so far…
Later on, they continue to use AP for string crossing when introduced to 3nps modal forms. They either continue to organize phrases to be geometrically advantageous, they intuitively(or now, intellecutally) develop a 2wps system to overcome the difficulties of AP, and most people still don’t reach the promised land.
Contrast that to what would happen if players are introduced to economy picking early on. What if they are taught early pentatonic licks with mixed notes per string and learn to incorporate sweeps and economy strokes?
When they get to 3nps scales, they might, instead of grappling with pick slanting, hopping, etc, instead resort to economy picking. [Aside: There are 100x more players who can riff on 3nps scales using legato than there are ppl who can do it with pickign. I think this proves my point that there is a knowledge/ability gap with how to pick these forms.]
My point is that an early introduction and reverence for strict AP (tremolo) causes problems later on. AP is not suitable for playing many phrases and the whole pickslanting thing is at least partly a kludge to overcome it.
How about this as a compromise: Early on, players should be given equal exposure to economy picking and taught that it is more effective than AP/pickslanting for many things that they will endeavor to play later on.
Look at Rick Graham to see what happens when someone has a great command of economy picking.