Gohan had to beg Goku to go full power, unlike 17 where he was forced into Blue when he didn't really want to use it. Goku took no damage from Gohan's 2 hits and then knocked him out flat with kaioken out of respect for Gohan's request to go all out. I see Gohan as somewhere above SSJ3 but definitely not a real serious threat for SSB. Now Frieza is also in the space between SSJ3 and SSB, the question is how much stronger Goku got after RoF and how much stronger Golden Frieza was than RoF Goku, and since that's complete arbitrary bullshit that can't be answered I'm gonna go with I feel is more likely in that Frieza is far closer to current Goku than Gohan is especially since his stamina issues won't be an issue since he's dead. Frieza is being portrayed as a rival to Goku here while for Gohan they went full Icarus imagery for him, he aint there yet, but maybe one day.