Yeah, I highly doubt they'd take the vague canonicity of a mobile game into considering, and even if they did it'd open the door to considering how GER had no effect of World Over Heaven into the matchup as well.
I think they should just stick to the manga, the anime and official guidebooks when scaling GER because if you start going into questionable canon territory it can quickly spiral out of control.
Say if you use Eyes of Heaven to scale GER, so RTZ now gets beaten by reality warping. Okay then, you should also be able to use Stardust Shooters then as that also has arguably canon qualities to it, so GER can now reset defense to zero. But GioGio's Bizarre Adventure for the PS2 was literally based on the Part 5 manga and closely follows the story events so that should arguably be canon too, so GER now completely no sells Time Erasure and can beat the piss out of you within it. But also Last Survivor had the anime closely working with it, even having it in it's Japanese title, so that can be arguably canon too. GER now has complete invulnerability to all forms of damage. Hell, Araki did some official artwork for the Jorge Joestar light novel and endorsed it so that could have canon qualities to it too.
GER can now blitzes Made in Heaven and characters like him, no longer needs to hit you (let alone kill you) to activate the death loop as GER only needs to swing its fist now. GER can also BFR you into a void world where life and death no longer exists, only 'nothing and nowhere' is in that world. GER can also explicitly nullify will so that you no longer are able to even
want to go against him. GER additionally can now nullify its own death to avoid said death and can exist in a place between life and death for 10,000,000,000,000,000 years.
That last example might have been a bit extreme but the point still stands. Death Battle should only use primary canon material (manga, anime, official guidebooks) to scale GER or else things get wacky fast.
edit: fixed now