This is my first post/reply because I too am new here.
I have a Graves Mk 1 faceting machine and I can assure you, it definitely has some flex to the quill.
I don’t know how much it will flex because I don’t force it … much.
But since the vernier scale is in degrees and there are no .25, .5 or .75 degree marks, I have to guess and utilize both the Fine Height Adjustment and/or a little bit of “English” on the quill to make my Meets meet. That is to say, I utilize the flex to a small degree.
BTW my quill assembly is 10.55mm in diameter !