This isn't true, a good friend of mine was a long time IV fentanyl/heroin user, when I introduced him to PCP and analogues he needed very little - 10mg of 3-MeO-PCE was more than enough to produce an effect.
I was the opposite, I'd do huge doses of 3-MeO-PCE but could be satisfied with very small fractions of what my friend would use as a recreational dose.
IMHO dissociatives are everything that opioids should have been. Better euphoriant, safer in OD, withdrawal is much easier, way better painkiller etc.
And several days to a week of effective treatment of depression in select populations.