Totally makes sense. Really your SI joint is connected more tightly to your shoulders than it is to your lower extremities! Solid sheets of muscle all the way up, and rib and spine joints that just don't bend in certain directions!
My DOM explained how these things tend to cross sides along the fascial lines. Right neck, left shoulder, right T-spine, left L-spine, right hip, left ankle. He says I'm textbook.
I'm hanging in there. Honestly except for a couple of sensitive spots (and if you've had tattoos you already know where they are), acupuncture is almost never painful. Occasionally the muscles will twitch or thrum a little bit, rarely they'll release in a major way, mostly it's just relaxing and energizing.
Hope you two are continuing on your recovery too!