Read the actual directive, and drill down. Basically, it's up to each nation to decide the categorization. And if you dive further down into that, the reporting requirements may or may not give you any but the most general geographical information, and very little to assess what the potential hazard might be. One example I looked at, for instance stated that certain chemicals were present onsite, but for a microchip manufacturer that could be a single bottle on the shelf - on the other hand, any bulk chemical processing facility might have tens of railroad tanker cars lined up. As far as I could tell, there may not actually be any on site, they are simply 'registered' to store it for use.
Another factor is that businesses startup and shutdown, so like all bureaucratic procedural information, what is the plan for continuous maintenance?
I see an interest to tag these sites as there are many of them and the information of public interest.
Other nefarious parties are also interested. So. the addresses in some cases are only the administrative 'home office', not the exact locations, which are to be given to the local law enforcement, fire, and other emergency responders - which makes sense because otherwise it would provide a ready target list for thieves and terrorists ( there is an entire federal agency division dedicated to this in the U.S. https://www.dhs.gov/cisa/chemical-security ).
> Any suggestion what tagging scheme to use ?
Use the tagging ( categorization ) scheme the regulatory agency themselves uses to classify these sites.