Hello,

I believe this bug (#28513) is a duplicate of #19412. In the discussion 
for #19412 I have investigated the problem and proposed a fix that 
doesn't require special-casing anything. However, due to being quite 
busy since then I have not had the time to properly test my fix. 
Briefly, the fix is to pass all the original args to the fallback 
function unchanged and then use "minibuffer-with-setup-hook" to simulate 
deleting the initial input and then typing whatever the user currently 
had typed into ido before they triggered the fallback.

I have rebased the patch from that thread onto the current master and 
attached it. To reiterate, this patch should be tested before merging.

Regards,

Ryan