I just created and exported a new font using Glyphs app.
While I was testing it, I realize how the style descriptor "Regular" appeared in the name as well.
Tried to fix this with Glyphs support as long as I discovered it's this way only on Illustrator.
No repetition on Photoshop or other non-Adobe apps.
Problem goes away if I have 2 or more styles, but other single-styled fonts (like Impact) don't have this repetition.
Might be a bug?