Some additional perspective regarding the ergonomics of the orientation. I think I can articulate why many ppl object to portrait mode:
I see what you mean regarding an increase in the moment on your hand(s), but that's only if you're pinching the iPad at the bottom. I don't find that position comfortable even in landscape so I don't hold the iPad that way. My preference is to put the palm of one hand under the device, close to the center of gravity. Then when holding in portrait the CG moves slightly up/away, so so does the palm of my hand. Slightly less comfortable but not a big deal.
But here's the rub. When in landscape, you can move your finger from the top to the bottom of the screen with practically only motion of the wrist. However, when in portrait you have to move your forearm to reach from the top to the bottom. This additional motion quickly becomes uncomfortable.
Btw, I get the business perspective for wanting one orientation for both iPhone & iPad, but unfortunately the ergonomic interaction with two devices is not the same and IMHO app design needs to take those differences into account. How many iPad users do you have verses iPhone? If the majority use iPad and overwhelming response is that portrait mode degrades the iPad experience, perhaps THT should consider jettisoning the iPhone app if your business plan can't support multiple interfaces.
Thank you and THT for all the hard work to roll out new features and trying to improve the Hopscotch coding experience