Christopher Awdry didn't do enough homework on his subject matter, did he?

Not only this, but the past few minutes, I've been wondering about Sixteen's concrete backstory.
He's got bits and pieces off several austerities. He's got the livery of Warrior who did work in Dean Forest, hence why Wilbert knows him, but then his fictional number belonged to-

another austerity called Walkden who currently works at the Ribble Steam Railway, in Lancashire.

Back to this thread, I was watching @TheBlueE21's content and he had the head canon that Sixteen was Sapper of the Avon Valley Railway, without calling him by name, funnily enough.

But seriously, I'd like to get this discussion on Sixteen's proper basis going.