Package format is only option in Keynote 6.5.3?

I'm wondering what's happened to the option to move between package and single-file format in Keynote.

For some reason Keynote seems to now only offer the package format. I create a new presentation, add a line of text and save, and it is a package.

In earlier versions there was a preference to change whether the presentation saved as a package or single file.

There is also a menu item under File > Advanced > Change File Type > ... that was supposed to let you switch an existing file between the two formats, but this option seems permanently greyed out for me.

Has the single file format just gone away now?

I realize if I have to transfer by 3rd party file servers I can always zip it up, but I'm curious if anyone knows the reason for eliminating the single file format, or is there something messed up with my fresh installation? I note the file type option is also greyed out in Pages and Numbers.