Such a rule can have the opposite effect though, a company may choose to hire/grow more conservatively if it is subject to a condition that it cannot layoff.
The comparison does not seem to be apples to apples. The perf gain seems to come from bundling the fork and exec call allowing the kernel to do vfork like optimizations. I think a fair comparison would be against a new sys call that does fork_exec vs io_uring_spawn, and not fork + exec vs io_uring_spawn.