Sorry, that's Utter rubbish!
Oh & it's .177/.22 not 1.77/2.2
It is only at sub 12ftlb that .20
has such an advantage purely because it is the fixed common denominator of the power level that necessitates the compromise of light & fast .177 or slow & heavy .22
When there is no power limit .22, .25, or even larger can come in to there own because the smaller lighter pellets cannot cope with the increased power as they all reach trans-sonic speeds (1100fps) at which point the shape of a diabolo pellet becomes unstable in flight, (speeds around 950fps are about the ideal max) & the larger/heavier pellets can whack up the power until they too reach this figure.
Webley quote that velocity because they make a stupidly heavy .20 pellet, (OK probably designed for the US market/FAC power) at sub 12 the only pellets to even bother with are the light weights,
if you go heavier than JSB's 13.5gn you lose most of the advantage of the cal, if you go up to webley/Crossman 14.5 gn you are in .22 weight and have lost all of it.