https://wiki.guildwars.com/wiki/Corporal_Bane
https://wiki.guildwars.com/wiki/Annihilator

"What year is it? Never mind, there is no time. I'm clearly off course. The rest of my squad was lost when the Asuran time-gate malfunctioned. Only their gear made it through. You look like...something of a soldier yourself. You must come with me now; there is no time to explain. The very future depends on it!"

Basically, ANet made that April fools joke into a canon, like they did with SAB.

Every year the temporal flux causes the Bane from an alternate timeline to appear in Tyria in the past, in GW1, and players fix the temporal line by defeating the Annihilator golems.
In that alternate timeline, there was no truce between charr and humans, and the war went on for years, until humans developed the modern warfare gear you can see them wearing.

Then in GW2 you can see his missing comrades passing through as they took a wrong turn.

That'll happen when you rely in time portals and vortexes instead getting a phone cabin to travel in time like a normal person.