Guard Dog aggression range should be 2 tiles
classic.runescape.wiki states this: "Guard dogs are very aggressive and will attack players from 2 spaces away."
In OpenRSC preservation server at least the ones in McGrouber's Wood attack from 1 tile.
All RSC+ replays I found the player was too high level them to be aggro.
I did find this YouTube video which doesn't mention if it's some private server or official Jagex. It looks like the player gets attacked from 2 tiles at 7:00 timestamp: https://youtu.be/3P-OMD2Lhcg?t=420