It's really about lowering cognitive load when making edits. It's not necessarily that someone can't figure out how to do something more sophisticated, but that they're more likely to get things right if the code is just kind of straightforwardly dumb.

The last two are definitely situational -- changing things like that might lower cognitive load for one kind of work but raise it significantly for another -- but I can see where they're coming from with those suggestions.

Even the camel/snake case renaming can be handled with the right regex, but dynamic identifiers are a mortal enemy. I remember the first time I came across a rails codebase... shudder