It's possible they tested touch screens with people using prototypes and whatnot but did not do their due diligence to test it long-term. On first impression, touch screens seem cool, futuristic, and flashy. It's really only when you try to daily drive the car that you realize they're annoying and a regression from physical buttons.
But, they present very well on sales room floors and car shows.
Then, a few people inside Mercedes hated the idea and forced a study group to prove their point.
Remember you have the stupid stuff that Tesla pushed hard during the peak Elon reality distortion field time. I regularly are in a Toyota, BMW and Honda, and all of these have well thought out touch/knob implementations.
This is part of the modern UI paradox. Never before has UI and UX gotten so much attention, and logging, and tracking, and research, etc. But of course with all that additional attention UI and UX is generally getting worse over time. I have my theories why, but I'd bet they're paying for decent talent here and are coming to the wrong conclusions.
... I cannot believe they actually put them in a base model Sprinter.
Do they hate tradespeople?