Smells fishy. Senior engineers in my knowledge and experience are all delivering on something relatively high impact while contributing massively to the team by occasional/often "pairing". I've seen rare examples who don't "pair" but just deliver by themselves. I've never seen an example where they don't deliver on anything (planning, design, architectures included) but only "pair" as their job every day.
You do realize that pairing is also delivering in everything you mentioned? Just because you hadn't the luck to experience this in your career so far doesn't invalidate this
But I don't sit over someone's shoulder at all times. I only try to help when I'm needed, otherwise I'm knee deep in my own deliverables.