Again, IMO. Judging from what I see in pictures

You’re right. If you want to confirm your suspicion for yourself, I’d be happy to loan you my Henson mild.

I’ve heard many times that Gillette made razors in order to sell blades.

I think that works for every blade format of Gillette except the DE blade, which was very quickly copied and Gillette had to compete unlike the later monopolies on patented cartridges.

I think the “big win” was with the band steel used for DE blades

GEM did that too with the double edge Micromatic blades. Single, spineless piece of band steel with an edge on either side and relatively simple cutouts.

Injector blades are single edge, but very narrow and probably don’t use much more steel per edge that DE blades of the time (they weren’t thin like today).

If you take into account that people used to hone even disposable blades to save money, the GEM format has a huge advantage over DE: if you sharpen a DE blade many times, the edge disappears behind the top cap and becomes useless. A GEM blade can be filed down several millimetre before the mechanism doesn’t push it all the way to the blade stops anymore.

I think the victory or the DE blade might be due to non-technical reasons. Better marketing and early market penetration?