when files are deleted via the user interface, this "frees up" the max file count for additional files to be uploaded. When files are deleted via API, the deleted files are still counted against the maxfilecount, and are not "freed up"

to reproduce:
run the attached web form.
do not select "delete via api" checkbox
add and remove a number of files.
good.

reload.
do not select "delete via api"
upload file A
select "delete via api"
upload file A one more time (note it will be deleted via api before it actually gets uploaded)
deselect "delete via api"
upload file B
note you can no longer upload files, allthough only 2 have been uploaded and maxfilecoutn is 3
bad.