Makes sense for them to support this given their scale. I wouldn't be surprised if GrapheneOS secures another big Android OEM vendor (after Motorola Mobility) and the user base of the OS quickly grows from its current 400k+ to millions.
Great news! I never had problems running Roblox on my GOS, but it's nice to to see the explicit, official support.
Snowball effect (for both sides, software publishers and OS vendors).
Seems ridiculous, but when their biggest rival can’t be bothered to support Linux… you see why they might announce something like this.