It means that casual players need to learn how timing rules work, and be clear during games when things are happening.
In regard to the ruling, I would say:
The runner cannot jack out. The runner inside jobbed a 1 ice server. Is it reasonable to expect that you would inside job a 1-ice server and then immediately jack out? No, there is no reason to do that.
Therefore the runner clearly was intending to continue onward.
The corp has the opportunity to rez Hokusai Grid at such a time that the runner cannot choose to jack out. If this is the corp's intent, it happens. The runner cant go back in time and say "oh wait, before you rez Hokusai Grid, actually I jack out".
Of course, the corp should have asked the runner if he continued the run first. However, in this case, its clear that the runner has no reason to jack out, since absoutely nothing has happened so far since he played the inside job.