Thinking about time fuckery leading Teshin to be flung into Duviri years earlier and in his first encounter with Thread, he mistakes her for Needle. Fully just spots her from behind, calls out to her, only for her to turn around and have the wrong colour eyes, no void markings or implants, and no clue who he is. Just a seemingly normal girl, albeit identical to his pupil and with a far lesser sense of duty or responsibility.
So I've started searching for Duviri fragments and it seems that the time fuckery is maybe canon? The Scholar's Landing fragment states that Teshin was found near death after his arrival in Duviri and that Mathila nursed him back to health, but he was then observed to 'deteriorate' with the passing of time (aka he was ageing, which the locals don't do on account of being storybook characters), so it seems reasonable that he's been in Duviri for quite some time by the start of the quest.
Meaning his indirectly referring to Thread as a temperamental child could well have been learned from experience lmao. I imagine that as he puts the pieces of her nature together, he attempts to mentor her but his efforts initially fall flat because he treats her too much like Needle, who had military training and had to be held to a certain level of discipline to avoid being deemed a risk and disposed of by the Orokin, whereas Thread has buried herself in a fantasy world in order to escape the horrifying reality of what she'd endured. They're both the same traumatised child, but one has been forced to compartmentalise and set aside her trauma to become a soldier while the other has effectively buried it in favour of play, so while his methods might work for Needle, they're more likely to alienate Thread, forcing him to adapt into the mentor he becomes in Duviri. No less stern, but a less harsh. Still demanding but with a wider margin for error.
