Yeah that surprised me too. Is it there so that when the finger stop moves, it registers the number? I've only had a few rotary phones in my life, but I've never seen one where that doohickey (which I believe is the technical term) moves.
The moving finger stop also appeared in 1960s versions of the Lineman's Test Set (the "butt set", usually hung from a tool belt), where the dial was on the back of the earpiece.
[1] https://en.wikipedia.org/wiki/Trimline_telephone
[2] https://www.bellsystemmemorial.com/images/dl/misc/schmoo.jpg
[3] https://www.bellsystemmemorial.com/telephones-trimline-artic...
A favorite example is the shape of a budding haploid yeast cell, known in the literature as a shmoo (though as that wikipedia page will indicate, there are a lot of other delightful schmoo/shmoo eponyms): https://web.archive.org/web/20071111122821/http://discoverma...
No. Moving to the stop is just to wind up the mechanism up to a defined point. After being released the dial turns back at a defined speed, and creates a number short on-hook spikes, depending on far it has been wound up - the number to be dialed.
It's possible to quickly tap the hook to dial a number, too. It's easy for low numbers, but the dial helps the slow ones of us to tap exactly 9 clicks in the defined time to dial a 9.
No idea if that un-smartphone works exactly like the real thing.