Diastimic also known as nonflux or orientationstable, refers to any orientation in which the intensity of one's attraction doesn’t change. A diastimic person is not aceflux, aroflux, etc. They may still experience fluid attraction, so long as they're either always allosexual or always at the same position on the asexual spectrum, only the gender(s) they're attracted to changes. It can be used to describe any form of attraction (diastimisexual, diastimiromantic, diastimialterous, etc.
History
Diastimic was coined by Tumblr user @anthropomimus on July 9th of 2018.
Flag
The flag was coined by Tumblr user beyond-mogai-pride-flags on July 9th of 2018. It has no confirmed meaning.
Resources
https://beyond-mogai-pride-flags.tumblr.com/post/175717289885/diastimic-pride-flag