It is regrettable that I was only notified about this after the ID change already took place, because we could have clarified things and involved the Mastodon app devs, and have some say in the matter.

Now clarifying an already existing API of ours would be exclusionary towards Pleroma. If you heard about our documentation changing to specify IDs as 64 bit numbers yesterday, it has been changed again today afternoon to keep Pleroma compatible.