In _fifc.fish:82, there is a bare rm … of the completion file generated. If you have a wrapping function (function rm; command grm --interactive --verbose $argv; end), this will be called, prompting for removal. Because the rm is in a completion function, there is no way to respond—and the completion file is not removed. This happens on every completion call (e.g., <Tab>).
This line should be command rm ….