Future relearning impacts on FSRS

Say I begin anki deck for a set of recently learned material.

I get to the point where the whole deck (say many thousands of cards) is in circulation, then work through material (either all material or some material) again outside of anki (books, videos, practice problems). If all material was externally relearned, I can’t see how this would affect FSRS algorithm too negatively other than reviews now showing, too early (in a roundabout way due to external learning). Alternatively if some but not all material was relearned I feel like this would maybe mess with the algorithm more than the former scenario. Thoughts?

Also what if relearning (all or some material) happened at a multiple points in the future - any additional considerations here? Thank you!