“Trouble is that ignores the bigger problem which is the arrival of thousands on boats that Europe goes out of its way to rescue”
Exactly. The entire strategy (if there is one) put forward by the EU is to deal with the migrants after they have landed. Where they are going to go, how they will be “shared” among the members (perhaps forgetting that they cannot be compelled to stay anywhere within Schengen), who should “process” them. The strategy should be to keep them out, to stop plucking them from rubber boats a few miles off the African coast and any that are “rescued” returned there forthwith. No amount of border controls will solve the problem because for so long as they continue to arrive, under the current strategy they will have to be accommodated somewhere.
“If they are not adhering to "free movement" does it make the confected NI/Eire border "issue" a red herring?”
It always has been a red herring. Neither the UK nor Ireland has any intention of imposing border controls on the island of Ireland and the EU has no resources nor any powers to do so.