To follow up on /u/paganach, we find very similar situations in ancient papyri from Egypt. There are different classes of papyri which are applicable, in this case namely literary and non-literary examples, and in both we find so called "slow-writers" -- that is, writers who are clearly very slow at forming the letters. In literary papyri, these are often assumed to be pupils who are being asked to copy out snippets of poetry or the like as practice for their reading, writing, and/or memorization exercise.

The literary contrast with non-literary (or documentary) papyri "slow-writer" (βραδέως γράφωv). These are often assumed to be adults (not pupils) who, for whatever reason, find themselves in a position to write lists, receipts, contracts, etc without the proper training in writing Greek letters. Such papyri often contain many spelling and (sometimes) grammatical mistakes, some of which seem to be the product of lack of formal education and some of which the product of being in a hurry (cf many spelling mistakes of my own, in this very sub or in this very post!). In many cases, it is likely that the writer is actually quite educated, but does not speak or write Greek well. In many cases, the write of the papyrus will identify himself as βραδέως (slow) on the papyrus itself, as if making an apology. In other cases, a surrogate writer was employed (a hypographeus) to write/sign the contract in place of a potential "slow-writer."