Mine gives 0.4 to 0.5% at 0 craftsmanship. % will go down as craftsmanship go up.
Your 0.1% will only be accurate at particular combinations of craftsmanship and recipe level.
This was my take on Green's post.
To the average person out there, Green might be right or I might be right, or we're both wrong. I can even say we're both close enough to the real value as well.

SE's statement is correct -> Increases Quality => Increases EXP + HQ Chance
Just that there is no definitive answer for "how much".