Why is it that Moses is not directly referred to as a Levite, as his bloodline clearly is of that tribe?
Just guessing here – perhaps because his position as leader of the nation outweighed his tribal affiliation.
I have a guess…
The argument was put forth by Aaron, and Miriam, that Moses was less than them because he had married a woman outside their tribe. eg: Read Numbers 12.
They specifically spoke against him BECAUSE he married outside the tribes.
Later, when God threatened to wipe out all of Israel, he asked Moses to become the only survivor; the head of a completely new people.
God had Adopted Moses in a special way. In a sense, Mose’s father has changed because God chose him; God spoke to Aaron and Miriam about this. Another bible quote is that Moses was told that he would be a “god” to Aaron. I think the writers of the O.T. may simply have wanted to avoid reducing Moses’ status. Eg: They don’t wish to disrespect him as a son of anyone less than Abraham.