I think this is another "what does the word mean" item.
Wikpedia Free Dictionary
Assumption
An assumption is a proposition that is taken for granted, in other words, that is treated for the sake of a given discussion as if it were known to be true.
In logic, more specifically in the context of natural deduction systems, an assumption is made in the expectation that it will be discharged in due course via a separate argument
Note the second part. That is what a scientific assumption is. It equates to a hypothesis. It gives the scientist something to work with. It is not a final solution.
Edited by bluescat48, : typo
There is no better love between 2 people than mutual respect for each other WT Young, 2002
Who gave anyone the authority to call me an authority on anything. WT Young, 1969