Actually, it's slightly more complicated than that. Diesel exhaust contains both nitrogen dioxide (NOx) and particulate matter (PM - which is basically soot from diesel engines). They
aren't one and that same problem. Each causes its own hazards to health.
I believe you are right in the sense that Adblue, as used as an additive to the diesel particulate filter (DPF), aims to reduce particulates. However the OP is talking about Euro 5 engines which don't have such an advanced design of DPF, and also emit a much higher level of NOx than Euro 5.
I'm no expert in diesel engine technology. But in case anyone else is interested, I found the emissions standards (in mg/km) for the various diesel generations:
View attachment 20944
It seems likely that policymakers will progressive regulate 'against' Euro 1-5 engines before eventually Euro 6/all diesels if they go that far.