The point for the legislation is to force market leaders to open up and enable competitors, today and tomorrow. Calling them out by name works fine for today, but won't apply to the next TikTok/Instagram/WhatsApp/etc.

Calling those companies by name would be extra stupid. Let's say out of nowhere there's a new company that fits to all the criteria but it's not called by name? The law would have to be changed to add their name to the law. It's wasting a lot of time. Instead of that there's a list of criteria and company is automatically on this "list".

well this is the way legislation works, it's considered bad form to call them out by name so you choose some few characteristics that apply to them which has the side benefit that if in the future some other company comes along with those characteristics the same laws apply to them.