My comment was rather related to the original point that someone had taken a seat other than their own. In such a small cabin I'd have expected that to be monitored, and the seatwalk/introduction part of keeping an eye on the cabin. Anyone that can't find a seat on a plane must struggle with life, it's not about being able to locate row 2 as being somewhere between 3 and 1, it's about knowing what's happening in the most premium cabin. The shown to your seat would be a polite passive way of ensuring people are in the correct seat.

Finding someone in my seat in economy is annoying, if I'd paid for first i'd be very annoyed. OP says in sleep suits, if that's the BA supplied PJs that's more than annoying, it's like getting a second hand experience. I think that's a poor show by the CC in terms of controlling the cabin, and I say that as someone with no knowledge of what they're supposed to do, it's just my thoughts on what I'd expect of first.