The reason I asked is I wondered if you had some specific theory why this would be so, or if it was just anecdotal.
There’s no technical reason why what you have described would be typical. In fact since amplitude is higher in horizontal positions, the opposite would be more likely (depending on the level of isochronism). There’s no direction I’ve ever seen from watch companies, or given to watchmakers in school or anywhere else, to intentionally adjust a watch in this manner. What positions run fastest or slowest is actually pretty random.
Cheers, Al
