This is what I've seen on older Ex's and Rangers in the salvage yard. The 96 and earlier trucks used the round filters and the round stamping was punched through to pull air in from the fender.
Every SOHC I've seen sucked air from behind the RH headlight though -- I'm guessing it was necessary for the SOHC intake design, or was just a coincidental rolling design change that began in 97.
It was surely easier (and cheaper) to pull the punch out of one section of the progressive stamping die and keep the rest intact than to rework the entire die. Since the bump was likely formed in an earlier progression than where the hole was punched, it stayed.