The watches we discuss here are often from the upper end of the spectrum. However this is often not everything offered by a brand. The annual production of Villeret pieces is a tiny fraction of Montblanc's total and on their own they are completely insufficient to keep the brand alive.
One could compare it to Porsche - no Cayenne or Macan, no 911. Or to a brand that did pull it off for a while, where the bookends were the Citroen 2CV and the SM.
The Summit will address a different customer base than the 1858 Tachymeter for sure, although there may be a small overlap.
As for Montblanc - probably the best brand of Richemont to try it out. I can imagine the upheaval if it was JLC, VC or ALS