First of all, why would they work on Galio this soon if their priority project is Warwick? Hell, a Rioter even said that they might look into Galio later on next year.
Second, Galio isn't a jungler. And Riot doesn't aim to make him one, so why make him a nature-loving hermit if he doesn't even jungle?
Third, by your logic, it could be Malphite too. Malphite's new VO could have a "rocky filter" as well. And how do you know this is Galio's voice actor? Their base voices don't even sound similar, and I would know considering that I'm a voice actor in practice myself. Don't jump to conclusions about things like that just because you want it to be.
Your logic is that Galio is an outcast from society (which he clearly is not, he's a Demacian hero and they practically worship the guy as a protector) and that he's a giant rock monster (which is also not true, judging from the art he's in he's at most 6 feet with a wingspan of 16 feet, so he's not as giant as you think he is. Malphite fits the "giant rock monster" category much better.
Also, seriously? Krugs grow like any other being. Pretty sure this mystery figure has cuddled with smaller ones, or maybe even is strong enough to cuddle with a normal one. Aso, Galio's title does not give him a "first name basis" with a common term given to guardians. The Blue Sentinel harbors a powerful magic force and protects it from thieves, and Galio, the Sentinel of Sorrow, is a guardian who is sad because he failed in protecting his master, but is determined to help those in need or sorrow. That's like me saying that Shyvana and Dragon are the same person because they're on a first name basis. "Dragonborn" and "Dragon" are so similar, Shyvana is actually Dragon omg illuminati confirmed!
Instead of coming up with false judgments and pushing them on everyone, how about you theorize like a normal person about who or what it could be? For example,
"I think that since this guy is a friend with jungle monsters, he's going to have fun times with the scuttle crab."