I don't think Goku & Trunks' gains can be linked to Gohan. We saw those two completely distance themselves from the future powerscaling, and having more longevity within the story provides the incentive for them to go far. On the other hand, Gohan was very much still within the domain of the future scaling, significantly below the top tier. Considering Gohan had trust that things would work out even if he died, it appears he thought of Trunks' development highly even without him being there.
It's worth noting that Goku did express killing intentions in relation to their fully-powered fight. The "Die Frieza!" line that I mentioned came while they were battling at 100%. Goku also said that Frieza's about to die as the all out bout was commencing.
We also saw that 100% Frieza could keep up with Goku in both hand-to-hand and ki attacks for some time. While Frieza is at his best, it wasn't a walk in the park for Goku no matter where his mind was.
@ScottyFamalam
It looks as though that mechanism -- or word of it -- was largely dormant/absent in the story, with a narrow scope of reference. When a Saiyan is rewarded from this in any meaningful capacity, it's hammered into the audience that a gain was made. SSJ Goku also wasn't near death, physically speaking.
