Not at all, for example you can't implement the ratchet down semantics of pledge() using seccomp. For instance having initial broader promise set "stdio rpath r

Not at all, for example you can't implement the ratchet down semantics of pledge() using seccomp. For instance having initial broader promise set "stdio rpath recvfd", and then irrevocably dropping to a runtime promise of "stdio" after init. This is a very paradigmatic use of pledge(2), which a large portion of the 85% of OpenBSD's base system pledged will demonstrate. unveil(2) would be very challenging, if not impossible. Both would require proper Linux integration and kernel implementation.