For the last 10 years, I don't think I met a lot of senior architects or dev who could understand all that.

Companies loves to have "specialized experts" who skilled up in one afternoon in their field. It might be different in startup, but in consulting world in relatively large enterprises, it's just a fucking joke.

Really? I think that in most orgs up to medium size, you expect senior and especially staff engineers to have that scope

They wouldn't be able to draw it all onto a whiteboard from memory. But give them a half day and they will have mapped out the data flow