Thank you. But if I passed eligibility so got pre arrival, would they need additional docs? It feels like the additional docs request is right, but the accompanying letter is wrong.PAL means you passed the eligibility requirement and the assessment of admissibility will start, and the medical request is part of admissibility assessment, while the other one is background check, which includes criminal and security checks. So a big congrats on this note.
As to the complications, just call them and let them know they have made a mistake. this is going to slow your processing a bit, so I recommend call them now, as there is a time limit on the request.