Those people would be dumbass kids on Reddit who don’t understand how steroids work. A theory I have heard before is that because something has a greater binding affinity it will make things with a weaker binding affinity “lose the race” to getting a spot on the AR.
So as an example, taking test with Tren is a waste, because Tren would bind more readily & displace it at the androgen receptor. Anyone who has ever used steroids knows this is total bullshit. If you take 350mg Tren Ace solo, or that and 500 test, which cycle gets you bigger and stronger?? The one with 500mg more gear, obviously. This is because the body upregulates production of new AR in the presence of greater circulating androgens. You can never saturate them all, because the body keeps making more as more stimulus is produced. There are other genuine rate limiters in place that are actually responsible for diminishing returns with increased dosage/duration of exposure.
Of course it’s true that binding affinity is very real, and some compounds will take a backseat in effect to more powerful ones (don’t expect to practically notice the addition of 3mg Ostarine when you are already on 15mg Rad, as a relevant example to our beginner SARM-using crowd referenced above). But you need to remember that a lot of that crowd is inherently inexperienced (why they only dabble with SARMS). That’s not a group you want to generally take advice from.