The communication overhead should not be constant - it should be proportional to the scope of responsibility.
As a full time senior engineer I’m responsible for oversight and guidance on three separate work-streams, so I have to go to all their meetings. If I were part time then I could be involved in just one of them, and go to only those meetings.
Hr setup/issues, all company meetings, team meetings, onboarding to company specific tooling, keeping up to date with team strategic direction, manager 1on1; none of these scale with responsibility.
As a full time senior engineer I’m responsible for oversight and guidance on three separate work-streams, so I have to go to all their meetings. If I were part time then I could be involved in just one of them, and go to only those meetings.