I know it doesn't suit your narrative but 'the RDG' has no contractual or legal right to decide on how TOC set fares are calculated. It did not remove the automatic rule because it 'decided' to; it was removed because is was resulting in fares at odds with what the TOCs wanted to charge.
In other words, in selected instances (seemingly of RDGs choosing) any TOC can just decide they want to charge more than the going rate, and RDG capitulate.
Just like when Virgin Trains decided they didn't want to allow Sheffield to London to be valid via Tamworth; within 24 hours it was no longer possible to book tickets priced by other operators, as RDG simply did as Virgin told them to do, despite in other instances denying the power to do anything.
A fundamental problem with fares in the past couple of decades has indeed been that there is no-one in overall charge, that is a result of the dysfunctional approach to handing fares setting over to multiple TOCs with an overarching requirement to produce a national fares structure but no effective mechanism to manage it; but that still doesn't (and didn't) allow ATOC/RDG to act outside the the scheme rules and in the order of things it is subservient to the TOCs.
... to the TOCs who shout the loudest and demand that they be allowed to circumvent the system and charge more, you mean.
In any case, the narrative from those who defend RDG often seems to change from "nothing can be done" to suddenly justifying unilateral decisions where RDG capitulate based on one TOCs demands. The result is nearly always against passenger interests. Funny that, isn't it?
The (re)construction of an overall body to operate and manage the network in GBR will address this but it's going to take some time to put it all together in a fully functional form. Then there'll just be one body to complain about rather than lots of them.
Unfortunately, unless that body is truly accountable to passengers, and truly has passengers interests as their priority, it risks being even worse than what we have now!
I really don't see how the TOC who complained about the long-standing rule regarding add-on fares had the power to not only get RDG to remove it, but get RDG to immediately delete the relevant page. Someone at RDG doesn't have any form of backbone whatsoever.
I'm not interested in hearing excuses for the behaviour of RDG / TOCs and anyone else in cahoots with those who seek to act against passengers.