That is great, I generally write watch movement repair on the watches I send out with a brief note in the package stating that I have fixed the watch but it was no where near as good as that one.
I thought the same. This post while it had very good intentions, can go the other way too. I send mine out as old watch for parts or repair. (Old is subjective and not necessarily a lie either. ) Or pocket watch for repair. Never had an issue and never needed an invoice.