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.
Also these activities might not always result in a lot or any artifacts. E.g. being in a meeting, making sense of messy stream of requirements and using institutional knowledge to help set the right priorities on a project or prevent team from spending months on a dead end idea might not leave any paper trail at all.