I don't know as we haven't even started with being gluten-free yet but this is something I will be watching very closely. (My youngest son has a biopsy coming up and the rest of us are scheduled for blood tests)
My oldest son has been diagnosed with Dysgraphia (which is essentially a disconnect between his brain and his hand). His handwriting is horrible. He's a freshman in high school and his little brother, last year in preschool just learning how to write, had better handwriting than he does. It affects quite a bit. I think he's learned to compensate for some of it but not all. A few of the issues that he has:
When writing (and really I'm talking just printing...there is no cursive at all) there are no spaces between words. Like he never learned finger spaces even though he did.
When he was younger and they did spelling and things like that....you could have him do his entire spelling list orally and he'd get 100% of his words right on the first try. Using the exact same list and doing everything the same except giving him a pencil and paper and want him to write the words out? He'd be lucky if he got 5 words out of the same long list. It's like he has to focus too much on forming the letters that the word just gets lost.
He used to go over the same part of a letter or a whole letter so many times he'd rip through the paper. I don't think he was even realizing he was doing it. It isn't always the beginning letter or the end letter, either.
His coloring skills suffer in a similar way and are also trumped by his kindergarten aged younger brother.
So....all that to say....given all the crazy symptoms I'm reading that Celiac's can cause, I don't think it's silly at all. There was one...ONE worksheet/writing task that a teacher of his showed me when he was in 2nd or 3rd grade that had awesome handwriting and I never could figure out what was different that day. He's also diagnosed with ADHD and ODD (oppositional defiant disorder). We did a bunch of testing on him in 2nd grade and he tested off the charts in everything but we were told that due to his handwriting issues and the fact that no one could read what he wrote...they couldn't put him in any of the gifted classes because they didn't have that concrete proof of what he could do.
So, I am hoping that being gluten-free does help clear things up some. Good luck to you!