Back in the days of Elmer Keith experimenting in the .44 world, 12 brinell was "hard cast". Now, that's just slightly harder than your average clip-on wheel weight. Many manuals talk about casting with linotype (about 19 brinell). While it's a really nice alloy and makes purty boolits, the high antimony content makes them fairly brittle. Most manufacturers will take something similar to a wheel weight alloy and water drop them straight out of the mold to heat treat them (arsenic required, or you just have wet lead), or heat treat them in an oven. Most commercial lead boolits will be around 18 bhn / brinell hardness scale, but they won't shatter on a deer's shoulder blade, for example.
What's really interesting is that you often don't need something that hard. It's part demand of an ignorant market and partially a fix for improperly sized bullets that don't fit the bore (the #1 reason for leading of barrels).
I don't doubt Mr. McNett's statement. That's going to drive a straight line very deep in an animal.
As far as shooting lead in your Glock, there's only one way to find out. If you don't want to try, but desire a "woods load" that acts like a solid, use a fmj solid.
To answer your question, those are beyond what I'd call hard cast.