Absolutely - in fact, using the presence of offset to indicate *I'm a footnote* was just a practical solution since I am sure some projects won't *always* want annotations to become footnotes, and with this check wouldn't need to specify explicitly *when* and *when not*.
However, maybe it would be best to go ahead and use a global boolean ((true) annotations always footnotes (regardless of offset), or (false) only when set in each context-mod to true (which could still be taken from offset's presence to avoid an additional/separate indication - at least while automatically-placed offsets don't exist). That may be the more appropriate way to handle it.
Hmm, intelligent/automatic footnote offsets - that sure would be nice.