That is true that several Ionity chargers may give reduced power. I experienced it myself. at Cobham.
However in my experience it it typically the car that causes slow charge and not the charger itself (yes, I know there are exceptions!).
I drive Kona and I know that driving @70mph does not heat up the battery significantly (I measured it with TorquePro at least 20-30 times on long trips). Often I drive 900m route and my first stop is after 172 miles (Ionity Dresden) - I usually arrive with 2% left (I know it is close

). Driving constantly @70-75mph for 170 miles raises the temp of battery by about 2C above ambient. As a result I only get about 56KW on first charge. Contrary to that, rapid charging raises temp to nice 25C! So all subsequent stops are much faster then! Always!
Also, if I arrive with
not low SOC (eg. above 25%) then charging will hardly ever ramp up in winter. It very, very often takes the same amount of time to charge from 35%>80% as from 5%>80%.
When I use 50KW Instavolts in winter and SOC is around 35-40% I initially get 34KW which then drops to about 25KW. When I arrive with 5% I get between 30-40 KW initially which ramps up to about 45KW after 10 mins.
It is usually BMS that tells charger how much to deliver. I actually find Ionity way more reliable than anything else and also in good locations. Relying on others - Allego, Shell, etc is asking for trouble - especially because there is often just a single charger.