get that its all roses and works perfectly for "low power" 5V only devices, that is the problem as it is a convenient "out" or shortcut for the junk suppliers to meet the regulation in wording but not in spirit. Your 3A 5V result assumes the charger has USB-C, which isn't being mandated!
The EU mandate is allegedly about making people reuse their chargers across more devices. But not all devices will charge with only 5V power. So if they only mandate the device connection end, we will still end up with many incompatible chargers as more dumb 5V <1.5A (anything higher requires some negotiation) supplies are produced and shipped.
I think it will work better than you expect. Existing non-C chargers will just work the same as they do now, and any new 'cheap' minimal-function chargers ditto. But phones and stuff will require more power than these chargers can supply, and over time people will buy chargers that work with their devices properly. So when the difference between the chargers is 6 hours vs 1 hour to charge a specific model of phone, the users will migrate to buying the more powerful one. Just as now you buy the quick-charger that's compatible with your phone and not the one that isn't. But you can still grab some random one off a shelf and use that in a pinch. The difference is that the phone-specific charger is now going to be a generic one, so you're more likely to splash the cash since it will work with your next phone too, whatever that happens to be.
What I haven't caught yet, unless someone has resolved it, is what happens to wireless chargers. The upcoming regs affect only wired ones, so will wireless chargers with captive plugs (or plugs with captive wireless chargers, if you prefer) be OK? That seems to go against the regs, and I would have expected a mandate that wireless chargers should be powered from a USB-C source. That may seem a trivial thing right now, but wireless charging is the future, if not already the present.