My headcanon is that OSRS is an alternate timeline branching off because of some difference during the God Wars. A small, but significant difference that caused things to proceed similarly to the RS3 timeline, but with some differences.
Just what all those changes and differences are has yet to be determined, as the known differences raise more questions than they answer.
Does Zeah exist in the RS3 timeline? Did it ever? Is it still around, or did the dragonkin or the God Wars destroy it in the RS3 timeline?
The Staff of Armadyl appears to exist in the OSRS timeline, but does it have power? Is it even the real Staff?
The Stone of Jas, according to lore found in Melzar's Maze, and to the Oracle, exists in the OSRS timeline, but is it still on Gielinor? Is it hidden in the same place, or somewhere different?
I think it's clear, however, that most of the backstories are the same (i.e. Guthix ended the God Wars because he had seen them happen before on his own homeworld and was horrified to see them happening on Gielinor, Zamorak's motivations for betraying Zaros, and so forth). So yes, the characters and their motivations and goals and so forth are the same. It's just that some things might go differently due to various elements.
Oh, and it's clear the Eastern Lands exist in OSR3 because of Shanomi of the Warriors Guild and the trader in Phasmatys.
15-Sep-2016 14:56:16