Well, a headlight bulb filament is close enough to a point source that it works pretty well, positioned and oriented properly. Modern low beams have very sharp upper cutoffs. Some of the latest aftermarket LED based bulbs have a pretty small effective source too, but I don’t know of any certified for halogen fixtures yet.
” positioned and oriented properly.”
A filament, say a single linear one, if it were horizontal then the vertical extent of the beam could be sharply defined while the horizontal wouldn’t but that doesn’t matter much.