When I see distance runner speed talked here, it's usually referencing 400 times, not 100 or 200 times. I doubt most distance runners have trained their speed enough, and raced enough 400s, to have 400 times representative of their 400 ability.
Sub-45 track guys don't run only 10% slower their first times out. Wil London only ran 57 in his first season. Other sub-45 guys like Verburg and McQuay ran 50-51 in their first seasons. All those guys presumably were doing a lot more things to develop that speed in those first seasons than most distance runners will ever do. Then they knocked a further 6-7 (or 13) seconds off with further development.
My own 440 yd best is from my second or third high school meet ever, a relay leg on a dirt track, having never trained for speed. I split 59.7. I never raced a 440 or 400 open, and never did another relay leg of 400 or 440 either. Does 59.7 represent my real 440 speed? Of course not. I have no way of knowing now, but I think I could have reasonably expected to work that down to 52-54 range if I had decided to do sprinting instead. I don't have an 800 PR because I've never raced that either.