When I first tried Hills I did the same thing and thought the same as you. I found that it has a lot to do with the file and the control of the file. The first improvement was to make a broadhead/arrow holder, simply a 6" by 1x11/4" chunk of ash that had rounded sides and a slot for the arrow to run in and the head was supported so that it would not twist when applying pressure. Second was to get Grizzly files. The narrow sides do no have the mill grid they are round and the milling comes to an abrupt sharp edge. The round narrow can be used as a mild steel, while the sharp corner cuts a more refined serration. With a Hill I get them as sharp as I can filng, then hit them with the round side, concentrating more on the right hand side and just trying to get a good flat bevel on the left side by filing into the blade, front to back. Getting the bevel flat is important and not having any roundness. then I do just as the Hill instructions say. With a 140 grain head that my son had mounted on a 2018 I sharpened one of his broadheads that way. He declared the head to be ruined. then that day he missed a deer with one of his shaving sharp,with a Dremel tool, heads and grabbed the one I ruined. The arrow ripped through the deer angled high lung to slightly center from a steep slope. The blood could be seen spraying in the afternoon sun. The deer went about 60 yards and dropped. The next year almost an identical thing happened, he stalked up on a bedded doe and missed with an El Grande Grizzly, this time he intentionally grabbed the arrow that I ruined for the second time and blew it through both scapula and out into the switch grass. He was sure he was going to miss a moving deer at 15 yards, but he did not. That deer went about 45 yards and was found in a huge pool of blood. I will admit to the same skepticism, but the results are what they are. We have never lost a deer hit with a serrated file sharpened Hill with either the double bevel or our favorites, the custom made single bevels. My own personal opinion is that the sharpening method works much better on a single bevel head, most of our 160 grain Hills were bought by our group by the pieces and we had the blades ground to a single bevel left wing for the left wing shooters and right wing for the right wing shooters. With some diligent practice, I found that there is a difference between keen and merely rough. If in doubt, with the use of a Dremel tool and several of its various tools, they can be made shaving sharp with some effort and that has worked just as well for us.