I have an m-1 from 1994. Came with a mag extension to put 7 in the mag. Plus one on the lifter and one in the chamber for 9 total.
For the lifter trick, after loading a full mag tube, you retract the bolt-- but only so far. If you go too far, the lifter pops up to load a shell. So retract the bolt only enough to drop one round on the lifter and same to stick one in the chamber. I cant comment on the new guns, but dont know why they would do away with this.
Also, if you load the mag, then hit the shell release, it puts one on the lifter, bolt closed on empty chamber. This is how I store mine. So if something goes bump in the night, just cycle the bolt and you are ready to roll. You might try this test on a new gun. Put a snap cap in the mag, hit the shell release to put it on the lifter, then cycle the bolt. If this works, then the you should be able to load one on the lifter, chamber and full mag.
TJ