Just to add what I mean by proven or covered, this is specifically the brokerages not the hedge-funds.If there is a certain amount of failed to delivers you get put on the list, the SEC acknowledges there may be a potential of abusive practices such as naked shorting. There may be a process if it makes the list a certain amount of days then a 13 day process triggers that the failure of delivers need to be proven to be covered or something like that (going by memory)
At minumum it shows the AMC Apes potentially are not tin foils Apes and that the government is also concerned about naked shorting this stock.
Also keep in mind there are other types of failure to delivers, legal reasons but being on the threshold is a red alarm of other things such the potential of naked shorts due to the large amount and having it happen on more than a couple of days. (no source, but verify everything I said it may be inaccurate but should be about the gist of it)