Interesting that it seems to tuck in well. I like IH shirts but find they do not. That has kept me from buying IH sihrts lately because i dislike the bottoms hanging out below the jacket hem.
Funny, you should mention that! I wanted a tuck-in denim and IH is too short and too "bunchy". The SJ is cut quite long (and also with that "apron-like" shape of dress-shirts to avoid excess material at the sides. It tucks ok, but you feel both the stiffness and the richness of the cloth. Both will gradually get better with break-in, I am sure.
I really can recommend trying SJ out, especially since you are US-based and can avoid the extra for customs/VAT. If you scrape away the social-media hype about woke-ness and community etc. (which I DO like, don´t get me wrong, I just find it a bit rich at times..) you seem to get a great product.