The rubric says for sourcing you need to tie it back into your argument. Another point is supporting your argument with the document. If you tie your sourcing back to your argument, does that score both points, or do you need a separate sentence for the latter?
I’d always stay on the safe side with two separate sentences. Good writing will, to your point, sometimes blend the two. But, better to “signpost” your HIPP (or HAPP) analysis right after you explain, or tie it back (if you want to use sourcing to begin your explanation) to nail it down.
One suggestion would be to use a complex or compound-complex sentence:
Given that the POV of Doc 1 is ______, it’s important to note that he ________; clearly, [EXPLANATION].