Personally i feel like both sides are correct.
Since higher Ki Control do grant Damage Boost to Ki Users, which allow them to amplify their attacks higher than their regular level, which its clearly show with Piccolo & Goku VS Raditz, meaning Cell's Solar Kamehameha should work in the same way.
But i do also think that this isn't limited to just their energy attacks, as nothing stop the characters to apply the same principle to enhance their physical attacks (the Dragon First or
this show that it can be done), and the same can be apply to boost their defense (an example may be Piccolo when he sacrifice tto saved Gohan from Nappa, yes he died but was still able to rise his durability high enough that his body wasn't completely destroyed).
Of course this requid time to charge as Ki Users still can't instantly focus all their energy in one point, other the fact that it probably consume a lot of stamina.
So Borutonarutodebunked's propose to have Cell and Gohan at '
4-B,
higher with Ki Control/Ki Amplification/charging' for not just Attack Potency but also Striking Strength and Durability make the most sense to me.