Oh, yeah, the real time when I found out and had the epiphany of just how important routine and familiarity are to Si dominants was when I went on vacation with the ISTJ and he spent the entire first two days really grouchy, grumpy and just not getting into the spirit of anything and wouldn't do anything, just complaining constantly. When I gently asked him what gives, he said, as if it was the most obvious and understandable thing, "Well, you know, I've never been here before, it's all very new and different."
I'd have understood if we'd been in like, a Buddhist monastery in Thailand or something, but we were only about 60 miles from where we lived, it wasn't exactly exotic. But it literally took him two days to 'settle in', to establish some precedents for being there and a sort of routine, before he could enjoy the vacation at all.
I still find myself stunned and amazed whenever I think on that.