I won't repeat what everyone else has said, as it's been summarized quite well.
I'll just add that the Super Tourer and upright-bar variants thereof were probably the only bikes of the time that made sense to come from the factory with stem shifters -
in their era.
Mind, the moment thumbies came onto the scene, stem shifters became irrelevant, IMHO. I still avoid them today, even on upright bar builds. Yes, stem shifters make a lot more sense on upright bar builds than drop bar builds from an ergonomic standpoint, but they're
still not ergonomically friendly when upright - shifts at near instant of desire are not a thing, and it stinks in an urban environment (YMMV in rural areas and quiet towns).
Personally, I find there are too many nice options in modern thumb shifters today - even though very few of them look C&V - but they're so much more ergonomically friendly that I'll give in to them if I have this choice to make. Case in point:
This is IGH, not derailleur, but I knew I wanted under-the-bar thumb-and-index finger control of all shifts from the start, and even the choice of a Nexus 8 was predicated on the need for there to be a non-stem and non-twist shifter available for that hub that would fit the bar and not come off as a huge wart. Luckily, Microshift did have this option, which I still think is a bit ungainly, but it works.
-Kurt