Whoever is originally responsible for the first pieces of small primer .45 brass is a short-sighted moron.
Actually, he was a competent engineer working to a specific end.
The FIRST pieces of small primer .45 brass will be found with an NT headstamp indicating lead free priming compound (and non lead or 100% jacketed bullets.) The Dinol mix used in those is so "hot" that the first generation Winclean used large cups but had to have larger than standard flash holes to vent all the fire and pressure into the case. That scared a lot of reloaders, too; but at least Winchester said they were ok for standard reloads. So they went to small primers to use less Dinol which gave adequate ignition and cost less.
There is now small primer .45 with no NT headstamp.
I don't know if those are lead free and just not marked or if they have gone to using standard lead styphnate small primers for convenience and cost savings by only having to run off one size primer pocket. And I don't know a cheap way to find out.
It is not (YET) a factor here. I have picked up two batches of small primer .45. One I used for experiments to see how much velocity was lost going to a small primer reload. (25-40 fps depending on the powder) The other had crimped primers to boot so they went in the scrap brass box.