I do not have any facts, as a matter of fact I don't believe anyone does on the this matter. But, I have heard a story.
...
...
And then there is another story that the Hmong language originated with the Green dialect. This is so because a lot of Hmong culture is in the Green dialect. When one "piav qeej" it in Green. And, a lot of our fantastical characters have Green names; like Yawm Saub, instead of Yawg Saub.
These are stories, and as any story goes there may be some truths to it, or it can be totally fictitious. It is up to you to decide.
The
facts can be found/researched and meticulously analyzed, conceptualized, and concluded in and by all of the scholarships of Hmong/Miao research documented, taught, and acknowledged today on a global scale by all past, present, and future researchers - Hmong and non-Hmong.
Can you cite your "
facts and research" info regarding your theories/supposition? -

Even if they are Hmong/Mong individual(s) or folklore/tale(s) ("dab neeg"), just tell who and what folklore/tale(s) and I'd be more than happy to follow-up or check into them. (I am always looking to broaden my knowledge-base and data-bank on Hmong/Miao history etc. Ua tsaug.)
Also, not that I completely "
disagree" with you, but I "
disagree" with you regarding: 1) one "piav qeej" it in Green and 2) a lot of our fantastical characters have Green names; like Yawm Saub, instead of Yawg Saub.
I tried to learn "qeej" several years ago, and my "qeej" master "piav" (sang) all of the "qeej" songs in White -

Bottom line, this is all dependent on the "qeej" master or singer, it can be in either White or Green - not exclusive to one dialect. This also applies to any other Hmong art/custom, be it funeral or wedding including songs like "kwv txhiaj/lug txaj" or "paj huam" or "paj lug" etc.. Likewise, this also applies to "
fantasical characters'" names too. It just depends on who - Green or White - is telling the folklore or tale. For example, the "fantastical characters" of "Nkauj Iab", "Nraug Oo", "Nuj Txeeg", "Nraug Zaj", "Nkauj Ntxawm", and "
Yawg Saub" are all in the White dialect -

Unfortunately, I do not know nor have heard their Green dialect equivalent. ("Yawm Saub" is White by the way,

)