I'm with the OP in terms of stamping. There is never any harm in getting one and it can prevent problems later.

We traveled from the UK to Germany by coach only a month before the pandemic. The coach took Le Shuttle through the Channel Tunnel. Our passports were scanned at Folkestone, but only by Eurotunnel personnel in order to provide an outbound passenger manifest for the UK authorities. No one on the bus encountered a French immigration official. I found this incredibly odd because we've made the same journey by ferry multiple times and have dealt with French immigration officers at Dover in order to be stamped into the Schengen zone. (French immigration were always surprised when clearing a bus from London, to encounter two Canadians who spoke to them in French!)

We spent two weeks in Germany, the Czech Republic and Hungary. We then took the train to Zagreb. At the border (this was prior to Croatia's entry into Schengen) Hungarian officials demanded to know why we had been traveling in the Schengen zone with no entry stamp--all we had was a UK entry stamp from Heathrow. They claimed there was no record of our entry into France/Schengen in their computers. It took a lot of explaining and back and forth between the officers before they reluctantly stamped us out of Hungary and Schengen.

Not sure how much has changed because we haven't used the Channel Tunnel or Le Shuttle since. But the lack of stamps in our case was a big hassle.