My n=1 experience in my non-fast, non-competitive (triathlete masters groups, several) has been this has not be remotely true at all at my level of MOP swimming.
I’ve done this drill with various tri masters groups (2 groups and 1 tri camp week), and was surprised to see that in my limited looking around, I saw no correlation with how far any of us did in terms of the wall pushoff distance (no swimming) after the coach taught everyone the correct streamline position (I’d learned it already, but a bunch of folks don’t know that their arms have to be nearly behind their ears if you’re doing it right).
I basically couldn’t tell in the water by looking left and right who was ahead/behind, we were all so close.
For sure, though, once we started swimming sets, I recall that two women in the lane to my left who equaled my wall push (but swam a good 20+sec/100 slower than me), were always instantly dropped the moment I took one pull. We’d start the pushoff together, they’d be right next to me, equal in position, and after one pull, I was half a body length ahead. I wasn’t beating them through my awesome wall push.
I’m also skeptical that that super-streamlined position is realistic for actual freestyle swimming. I think it’s a good drill just to show HOW much more streamlined one can get in the water if you put your whole body into shaping it, but I’m certainly not doing that position in the middle of a freestyle stroke, ever - if you try and do it even with one arm while swimming freestyle, you instantly get a cross-over hand position out front. The much more realistic drill position that you can get during freestyle swimming is more of a superman position, without the hands overlapped in front.
Still, you def could be right - in competitive swim squads where people are all training hard and talented, so the gaps are smaller than what I’m seeing in my tri groups, some people might just be more hydrodynamic in the water through shape or trained position, and for sure that will lead to faster speeds. I’m just noting that it hasn’t been anywhere that clear when I’ve done this drill with tri groups of really varied paces, and that the people a lot slower than me are nearly my equal on the streamline drill (this could also mean either I have a bad streamline, which is less likely given several coaches have ok’d it in real-time for me, or that I’m just built like a tugboat rather than a seal, and that is absolutely possible, if not more likely!)