Some planes have a separate bug where it is not possible to add fuel to them via any method, even keybinding. Not saying that is what people are talking about, but it could be useful to list the planes people still have issues with to see if it is one of those planes. For instance, the AeroElvira Optica has a separate fuel bug, different than this one, that it cannot have fuel added to it via any means.
Perhaps test a common plane, such as the 172, to see if this issue is fixed. Then open up bug reports for individual planes if it is. I’m not dismissing people’s claims, just saying there are multiple fuel bugs so being specific can be of great help in identifying which one the user is running into.