There is a flag, if rarely used, for omniaromantics (people who do not feel romantic attraction, do not desire romantic relationships, etc. I'll let y'all read the definition). Found here.
It's been around for more than a year because we, as a community, recognize anyone who is gray-aromantic as aromantic, and belonging in our community. Even if some people did recognize the desire for a second flag, they wanted to keep the aromantic flag for our community as a whole: that's who it was created for, after all.
As a final note, I am what you might call a "true aromantic" or whatever somewhat offensive term you are using - I don't feel any romantic attraction, ever - and I think that the way you've approached this topic is slightly offensive at best. Creating separate terminology for aromantics who feel no attraction whatsoever is fine - I believe I've seen terms like "null aro" floating around, as well as omniaromantic and others - but doing so in a way that alienates gray-aromantics leaves a serious bad taste in many people's mouths.
In fact, it reminds me very much of the time when I was told that "arospec" was for gray-aros (including demiromantics, lithromantics, etc.) but not for null aromantics. It made me very uncomfortable - after all, I had been using that terminology for years, and it was part of my identity. People telling me I could no longer use that term for myself was a struggle (and yes, we did come to a consensus for the opposite conclusion, but it was a discussion that was had).
So while I understand you may want a term or flag for your individual identity, it comes off as offensive and rude to alienate gray-aros from our community and flag when they have been here since the beginning, and since the creation of the flag. It makes a lot of us (gray-aro or null aro) feel very uncomfortable with the discussion, and not in a way that produces positive results.
In conclusion: gray-aros are aromantic, and absolutely should be able to use our flag.