Too small? I doubt that. The likes of Patterson, Spinks, Jones Jr, Moore, Toney have all managed to have title winning success at HW despite being former LHW. Bivol and Beterbiev both 6 foot tall and probably weigh not far off HW come fight night.
Bivol only has a 72 inch reach and Beterbiev doesn`t fight defensively like the fighters you`ve listed, coming forward and trying to KO a heavyweight would be suicide.
Michael Moorer came forward and tried to ko plenty of HWs. There's just no way Ruiz Jr would beat Bivol or Beterbiev.
Ruiz might have beat Moorer, his chin was suspect and Bivol doesn`t have Moorer`s power. Moorer had a longer reach than Bivol and was a southpaw, Holy would have destroyed Bivol and Beterbiev.
Holyroids would also destroy Ruiz, what's your point? I don't put it past me that beterbiev KOs DoubleCheese Ruiz, he put Usyk down in the amateurs so why wouldn't he be able to put down a fat Andy who sits right in front of him? Also I see nothing about Ruiz that tells me he gets Bivol out of there in 12. He will get his short unexisting t-rex jab taken away from him and be made a fool by Bivol
Ruiz could have raded with Holy, he has a good chin and could match Holy`s power, Beterbiev has been hurt and dropped by light heavies and Bivol would not be able to match Holy`s power at all, Spinks hit far harder than Bivol does.
What weight class do you think Ruiz would be in if he was actually in shape and not grossly overweight?
That fact that even an absolutely idiotic question like this gets any sort of serious responses tells me a lot about the current heavyweight landscape than anything