There are some discussions about it, for example here:
I am personally convinced that lighter riders are faster than IRL, especially on the flat, but also on the hills.
Equipment and pacing also play a role, e.g. in today’s TT I was beaten by a lighter rider in every power metric, but I won on time:
Me (71 kg): 321 watts (324 NP), 4.5 W/kg, 23’54"
Another rider (69 kg): 329 watts (335 NP), 4.8 W/kg, 23’56"