not to stir the pot here, but there are more frame styles than just the drop-loop. excelsior, harley, and others had a "no loop" (dunno what the actual name is) frame where the engine was used as structural support, and the down tube was chopped off right after the headtube.
"period correct" gets thrown around here alot, but in most circles it means that all the parts are actually from that period, yet may not be a part offered by the manufacturer.
for instance, an aftermarket horn or light (or anything else) made in 1940 and installed on a 1940 bike, would be "period correct," even if the original manufacturer didn't install it.
trying to build a "period correct" 1900's boardtracker is pretty much impossible for just about everyone.
a modified worksman frame, home-built bike, or any other custom fabrication would just be a reproduction, a tribute, or even an interpretation of the original.
then there's the "boardtracker look."
i agree that just flipping over the bars on your beach cruiser and taking off the fenders doesn't make it a "boardtracker," it just makes it uncomfortable.
basically, with our "hobby," you can call your bike whatever you want, be it a chinese toy store bike with harley stickers on it (which, if ya think about it, is pretty much a harley replica, these days) or a custom built, drop loop board tracker.