I noticed that too. I use some other vinyl protectants (Armor-All water based) that also have this odor. I think even Meguiar's Natural Look has a slight BO smell.
Probably some common chemical that would otherwise be muted out by a stronger artificial scent.
From what I recall, you can actually cut 303 with water, so you might dilute it down for interior to make it smell less and to only add protection without the slickness.