I found that statement to be the most informative part of the document. It made me stop and consider it as, yes, I wouldn't have believed it until it was so explicitly pointed out.
Science is full of authors supposing what other people believe and then surprising them with their findings.
"Remarkably", "perhaps unintuitively", "convention states", "a striking consequence", "a surprising result", …
You may not believe this, but here's Feynman making assumptions about what other people think:
Because atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it appears peculiar and mysterious to everyone—both to the novice and to the experienced physicist. Even the experts do not understand it the way they would like to, and it is perfectly reasonable that they should not, because all of direct, human experience and of human intuition applies to large objects.
Here's Newton using "which is an erroneous Supposition", his version of "you may not believe this":
Are not all Hypotheses erroneous, in which Light is supposed to consist in Pression or Motion, propagated through a fluid Medium? For in all these Hypotheses the Phaenomena of Light have been hitherto explain'd by supposing that they arise from new Modifications of the Rays; which is an erroneous Supposition.
As Albert Einstein wrote:
The whole of science is nothing more than a refinement of everyday
thinking. It is for this reason that the critical thinking of the physicist cannot
possibly be restricted to the examination of the concepts of his own specific
field. He cannot proceed without considering critically a much more difficult
problem, the problem of analyzing the nature of everyday thinking.
How can you do that without making assumptions about what other people think?
> "Remarkably", "perhaps unintuitively", "convention states", "a striking consequence", "a surprising result",
are very different to "You may not believe this,"
because they don't say "you" they state it in a general way which is ambiguous about weather it was e.g. "remarkable" for them or many they know
so they don't make assumption about every specific reader, instead they make assumptions about themself and/or readers in general
The examples you state all are different and in my opinion miss the point. In no case do they say "you ..." or anything close to this. It's always in a genericway. In other words "even experts will find it peculiar", "theories of this kind are erroneous", "he - as in a generic scientist - needs to consider something".
Science is full of authors supposing what other people believe and then surprising them with their findings.
"Remarkably", "perhaps unintuitively", "convention states", "a striking consequence", "a surprising result", …
You may not believe this, but here's Feynman making assumptions about what other people think:
Because atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it appears peculiar and mysterious to everyone—both to the novice and to the experienced physicist. Even the experts do not understand it the way they would like to, and it is perfectly reasonable that they should not, because all of direct, human experience and of human intuition applies to large objects.
Here's Newton using "which is an erroneous Supposition", his version of "you may not believe this":
Are not all Hypotheses erroneous, in which Light is supposed to consist in Pression or Motion, propagated through a fluid Medium? For in all these Hypotheses the Phaenomena of Light have been hitherto explain'd by supposing that they arise from new Modifications of the Rays; which is an erroneous Supposition.
As Albert Einstein wrote:
The whole of science is nothing more than a refinement of everyday thinking. It is for this reason that the critical thinking of the physicist cannot possibly be restricted to the examination of the concepts of his own specific field. He cannot proceed without considering critically a much more difficult problem, the problem of analyzing the nature of everyday thinking.
How can you do that without making assumptions about what other people think?