What this person seems to be arguing is that scientists "try to prove a hypothesis", and so the process is biased in favour of positive outcomes.
Rather than that a hypothesis is "this is the claim/idea I'm setting out to test, and a positive, negative or uncertain outcome is equally valid/useful".
Comments
Sometimes, its tentative nature is seen as a weakness:
'even the researchers admit their study has limits'.
When it is a strength.
'I can see it with my eyes, they can't see it from the lab'.
Sometimes its the opposite and science is criticised for being too sure of itself, when it can't be, by design.
Rather than that a hypothesis is "this is the claim/idea I'm setting out to test, and a positive, negative or uncertain outcome is equally valid/useful".