So the teachers/schools could have given a rank without a mark and the outcome would be the same.

No. Let me try and explain why ranking was needed to allocate the final calculated scores.

Let's say it is thought appropriate to give a school 50% recognition for its teachers' assessments (TA) and 50% recognition for its Junior Cert prediction (JCP).

The obvious first attempt would be to give each student the average of their own TA and their own JCP. Two problems with that. Firstly not everybody will have a JCP. But much more seriously each student's LC outcome would be 50% tied to how they did in JC. This was rejected as wholly unfair and inappropriate and I fully agree with that.

But this would not be unfair in aggregate at the school level if the school was sufficiently big. So what they did was assume that in aggregate the school would perform 50% in line with the TA and 50% in line with the JCP. But not just in average outcome but in the whole shape of how individual scores would be spread about that average. This is what the statisticians call a "distribution".

Having thus determined the school's aggregate calculated distribution it remains to allocate calculated marks to individual students. This is done by slotting them into the distribution based on how they ranked in their TA.

So note that the inflation inherent in TA remains in this model at least to the extent of 50%. That inflation comes from marks not from ranking.

Of course one might have contemplated using 100% JCP, in which case you would be correct and the teacher ranking would be all that would be needed. It would certainly have eliminated grade inflation. Perhaps one for COVID 20