I've only seen round checkboxes used in the context of selecting multiple things in a list of indeterminate size, like emails in your inbox, photos in your gall

I've only seen round checkboxes used in the context of selecting multiple things in a list of indeterminate size, like emails in your inbox, photos in your gallery, etc. In my mind this is a slightly different application to the classic "form" that you fill out with data and options before submitting.