The problem, and it's the same with the Passat, is that the amount of ash produced is calculated based on the consumption of additives (?) and fuel (?).
If it were measured, there would be fewer problems; however, to achieve this, the car would also need to be told, "Hey, you have a new filter installed, please calibrate yourself."
At VW, we have the advantage of using VCDS and can reset this ourselves. I suspect that you don't have something like that available to you.
In addition, the electronic equipment at Citroën workshops (the ones I know) is more than just basic; I think the people working there probably follow instructions strictly out of fear of damaging something.
Audi A5 B8 Cabrio 2.0 TFSI/CNCD 225PS
Audi A4 B7 Cabrio 2.0 TFSI/BWE - sold
Passat Variant Highline 3BG EZ 2/04 2,0 TDI mit DPF 235tkm 2x DPF gespült - RIP dank LKW
Of course, it would be possible to make all the electronics much more intelligent.
But who wants that? It's all geared towards customer-workshop relationships, and therefore designed for exploitation. And this is just the beginning...
These days, if you can still change your light bulbs yourself without having to disassemble half the car, you're already doing pretty well!