I know a guy who was a Master Technician for Vauxhall. He says exactly the same thing. Dealer mechanics don't even get the time to do the job thoroughly, it's all about getting it done quickly so you make more money. His advice was that a good independent will do much better job.
The first time I encountered a digital service record was on a Mazda. There was no service book to get stamped, it was all in the Big Brother Mazda computer. I asked if it was possible to get work done by independent garages added to that record and they said no.
I started just keeping receipts and made up my own service log. I included not just servicing but a record of faults, repairs, MPG and included a list of consumables like bulbs and wipers so that it's a one-stop document for looking after your car. It worked so well I've done it ever since and buyers are totally happy with it. They can see that the car is carefully maintained and are not at all phased by the absence of the digital record.
I can send a copy of a record to anyone who wants to see what I mean or use it as a template? It's pretty simple.