I'm not sure why but questions around increasing the size of the biggest sprocket that a derailleur can accommodate have been much in my inbox lately - I'd hazard a guess that the trend for going up very steep bits of gravel has come at a time when money is tight and the only consumers with money are perhaps a little older but they still don't want to spend a small fortune - so they're looking to spend money to extend the capabilities of what they have, rather than starting from scratch ...
Hence, watch this space for an article to come, on rear derailleur design, specification and why derailleurs are designed the way they are and how, to work properly and predictably, they are perhaps not quite as simple as they at first seem ...
