Uneven saddle wear

[ASC1951]

I'm pretty certain both legs are the same length

Are you? It is quite difficult to measure that yourself with precision. I had exactly the same symptoms on my first B17, which I rode for many years before the physio pointed out that I have one leg longer than the other and gave me some stretches to compensate.

Am I a freak?

Yes.

Should I be worried?

No.

 

[Joe24]

Could be that your bike is off balance eg caused by bent forks, requiring you to exert more force on one side to balance it. If you can ride your bike free handed then your forks are probably ok

Could be the camber on the roads, i know what the Welsh roads are like, pretty pants.
Lazy Welsh