it isn't the receptor thing it is the hormonal aspect
when you run tons of gear you are only causing more sides, you won't gain more by using 2000mg of test vs. lets say 1000mg of test. but you will most certainly have more estrogenic and androgenic sides.
on the flip side yeah if you run 1g of test you will gain more than running a TRT dose. so this entire thing isn't black and white
the general consensus is 500mg of test is a good dosage and any idiot can make gains on that and sides can be controlled in most cases. so why run 2000mgs?