So three stories out of 200 odd, that's not very good odds. When put against all those stories when they don't say anything about it one way or the other.
That's still three stories that explicitly state Hartnell was the first, as compared to zero that explicitly state he wasn't. There's far more onscreen evidence that the Doctor's name is actually "Doctor Who" than there is that there were pre-Hartnell incarnations.
The argument from silence is a weak argument; you could argue all sorts of things about the world of Doctor Who from that point of view. Hell's bells, there's only about three stories out of 200 that state that Adric died, the rest don't say anything about it one way or another. Maybe he survived, travelled to Pete's World and inspired John Lumic to create the Cybusmen by recounting his experiences in Earthshock. There's not much in the series to contradict that either.
Come to think of it, there's only three stories out of 200 that support the idea that Paul McGann was the Eighth Doctor. Might as well toss that out too.
At the end of the day, it really doesn't matter to me if someone wants to believe there were pre-Hartnell Doctors, but I don't see any credible evidence for it.
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