Biden could approach and pay respects, but WAS NOT allowed to 'lay' the wreathe
For comparison, here are past presidents, actually elected and recognized by the US military as their commander in chief. Wreathe is presented for the POTUS to lay, rather than already there to begin with.
Here's Trump
And Obama
And Bush
And Clinton
And Reagan
Only Biden was denied the laying. Could approach and pay respects, but not lay it. Aligns with being a foreign dignitary rather than the POTUS.
Seems it's happened before, but the VP is literally no where in the chain of command. Just because he's first in line for the position of commander in chief doesn't mean he should be saluted anymore than the secretary of education for being 17th in line or whatever.