No, in the highlighted section he is explicitly saying you can't figure out how big the market is by reasoning and the best you can do is guess.
In fact, it is a bit stronger than that: he states that the only knowledge that can be used is instinctual knowledge, but since instincts concerns things like what smells indicate spoiled food and legless that animals are dangerous, you don't have any relevant knowledge at all! The best you can do is baseless guessing, though after having gotten funding and done a bit of work you might have some basis for your estimate (there is a caveat that instincts dominate estimates early in the start up process).
The summary ars provides does seem to be what he strove to say, but since two people can easily disagree on what is to be considered "obvious" even that statement allows for less predictive power that seems reasonable.
In fact, it is a bit stronger than that: he states that the only knowledge that can be used is instinctual knowledge, but since instincts concerns things like what smells indicate spoiled food and legless that animals are dangerous, you don't have any relevant knowledge at all! The best you can do is baseless guessing, though after having gotten funding and done a bit of work you might have some basis for your estimate (there is a caveat that instincts dominate estimates early in the start up process).
The summary ars provides does seem to be what he strove to say, but since two people can easily disagree on what is to be considered "obvious" even that statement allows for less predictive power that seems reasonable.