I think it's the width of the nose that is "sliding" me forward. Keep in mind the slope of the side of the saddle; so on each stroke of my leg, there's "more seat" to push me forward. As I said, with another saddle with a far, far thinner nose, I do not slid forward at all. THAT saddle had very little padding, so I got hot spots on both sit bones.
The actual issue is there's a nice "valley" in the meatiest part of the saddle for my "stuff" but sitting on the nose brings a tad too much pressure to said body parts.
It all has me thinking about noseless saddles. Or about raising the bars a tad, or some so I can sit more upright (even thought about a kind of bar end where I can position my hands 4" above my flat bars). BUT, my arms now are in great shape for laying out more... so it's all about satisfying multiple things, not all of which work in perfect harmony!