Most of the guns on that list are now over 50 years old, but they weren't when the list was first compiled, about 1970, IIRC. And of course at that time the 50-year rule didn't exist. As it stands, BATFE no longer adds any gun over 50 years old to those lists; there would be no point in it since the blanket rule covers them.
When GCA '68 was first passed, there was no 50 year rule, and the only way to get a gun of any kind designated as a C&R was to petition BATFE (or whatever it was at the time - ATTD, ATD, ATF, etc.- to declare it a C&R. And it had to be something special to pass the test. That is where those "6.3mm Blatz automatic pistol made for the Klotz Emperor's personal guard and bearing the seal of Klotz in gold" entries come from.
(The C&R designation was the result of some heavy lobbying by wealthy and politically influential collectors who had been trading with each other for years and didn't want to have to go through FFL dealers to continue doing so. The result was the 03 FFL and the C&R designation on firearms.)