Bitesize is another of those projects that died because however intuitive, inventive, daring or simply fun they were - they weren’t what the company wanted us to make. Also (always) because the platform we used (Sheets in this case), and the platform we were using it to replace (Sites) didn’t see what we were doing as genius. They just saw it as a bug, a backdoor, a security threat. A threat basically.
Which is, in my opinion, why apps should never leave beta and should always be ready to become something else.
There is no documentation on Bitesize. It was over an extended period, strangled at birth. It was sad. My thoughts and prayers are still with Jonny Richards and Jude Osborn