I also think that when using magic as a technological tool, one should consider how invention occurs: it is gradual improvement.
To stick with printing press, it started with carved cylinder of clay (I believe ?), then carved wood blocks, then individual characters in lead (but other materials where used until the "good" solution was found). And at the same time, the design of the press itself went from manually applying the carved cylinder of clay on a support, then a flat, mechanical system where a page or a sheet of support was imprinted (and finding out how to assign pages when printing a large sheet that would be folded afterwards), then the cylinder applying evenly pressure as the sheet rolls on the character.
In parallel, the writing support evolved, the inks, the ability to include image through several application of different colours (and different carved blocks).
Although magic can ease many of these steps, a gradual improvement of writing/copying feels organic - and also avoid a sudden technological jumps that would completely upset the economical/power balance: how would Durenmar justifies anymore the lengthy delay to get a certain books once this technology is available ? it will be a huge loss of political influence, so house Bonisagus (which technically swore to share its knowledge, but most sourcebooks show to be "difficult" to fulfill its oath) will take measure to prevent that, one way or another.
If gradual changes are introduced, it becomes easier to get buy-in from a larger audience, thus gaining allies against some hard-core opponents and gently pushing them aside instead of butting heads with them.
Regarding quills making perfect copies, there is a level of uncertainty: each quill will wear off differently, and the quality of the writing support will also be slightly inconsistent, leading to some letters being misshaped, a small hole, a blot of ink.
It is assumed that magic can repeat perfectly the movement, but how accurate is it when doing minute details ? maybe, the initial texts copied with this technology are larger, with larger characters - after several trials and errors the mage found out that below a police of 20 (to use modern reference), the errors starts to creep more and more.
It would require another improvement (steel tip quills? spell to control ink flow ? alchemically purifying ink) to reduce to a smaller character size (let's say 14).
To further reduce the character to 10, the writing support quality need to be improved, to be perfectly smooth. Possibly moving from parchment to wood pulp/bamboo/linen/mulberry fibers mixture (maybe a similar improvement from iron to alchemical steel, from wood plank, to supple paper sheets).
Pitch it like that, it is easier to get buy-in from a troupe, than going straight from Scribe to Xerox machine.