Small sample size maybe?
Who knows why people fly one plane in any given mission over the other. Friends they see in one craft, general independent random selection coincidence, etc. I'd say the Spit1 and Hurri1 are about equally popular in AH, nowhere near the 4.5:1 ratio portrayed in the screenshot.
The Hurri1 is noncompetitive against almost everything in the planeset, assuming a correctly flown planeset. I would estimate it gets at least 30% of its usage from people who ask "What's the best turner?" and are directed to it.
The Spit1, although also very noncompetitive, has a slightly larger dedicated flier contingent (spit dweebs almost have a union) and it at least can compete against some other early war craft in climb and speed (certainly not roll!).
You're absolutely right about how the Hurri and Spit were generally used in the Battle of Britain, although Hurri's weren't "bomber only", they actually did pretty well against the 109's when vectored that way.