The "buskadero rig" is a creation of Hollywood.
No doubt the buscadero"drop loop" is a 1920's invention used and popularized in/by 'B' western, as are the tie downs as a norm.
But Capt Hughes is credited for the first buscadero design that predates the drop loop by at least 2 decades.
A lot of those Hollyweird 'drop-loop' rigs had the drop loop actually made of sheet aluminum covered with leather. The holster, too, was actually an aluminum bucket covered with leather.
You see one of 'em placed on a bed--the best example is in the 'dressing scene' in Cat Ballou. Kid Shellene's double buscadero rig is on a bed. It pretty much stands up by itself. I'd have to bet there were usually 2 identical rigs--one with the aluminum inserts, one without. If you tied a pair of the aluminum ones to your thighs, B-movie style, you'd have real trouble walking.
At one time Tandy Leathe Company had a kit to make one of those things. You could trick out the leather with carving & conchos & then lace it in place over the aluminum. I never did make one of those. I made myself a police gunbelt that was decorated with carving, but I made it out of saddle-skirting leather.
I did make a tie-down holster for myself once, for a reason. I was wearing a heavy Colt New Service on my right side. We were having a lot of trouble with predators in our sheep & goats. One neighbor who had 750 angora nannies managed to raise 17 kids that year. Everybody went armed. The only time you didn't have a pistol on you was when you were on a public road. Then it went into the glovebox but you had a rifle & a shotgun riding in the rack inside the back window of the pickup. I had my pistol, Dad had a saddle-scabbard I made, with a .30-30 in it. He never was much for pistols, but if he could see it & it was in range of that Winchester, it was gone. We finally got a govt trapper in. He said our area should be supporting maybe as many as a half-dozen major predators. When he left he'd killed over 200 coyotes, bobcats, & lobo wolves. This was in western Williamson County, Texas, in 1960 & '61.
I put a heavy duty securing snap on the holster to keep the pistol in because I wasn't using it for fast draw. I found out something. At a trot or gallop, that holster, before I put a tie-down on it, nearly beat me to death! I got bruises as big as my hand right on my hip joint. Once I put the tie down on it the holster didn't flop around any more & I got no more bruises. Thst's the only reason I've ever found for tying down a holster.