That’s one interpretation.
Another is, the free trade zone between all four countries in the UK, and the Republic, has existed far longer than the EEC’s free trade area. Dublin is the party that insists on having its cake and eating it - by insisting there has to be a customs border between GB and RoI, despite not wanting that the border to be located between it and the North. Because that has to stay open.
It’s an irrational imposition hiven the EU knows 99.99% of all UK standards remain completely unchanged since Brexit. If we’d suddenly binned those standards then there’d be a point to it; as we haven’t it’s just an artificial creation of a customs border that serves no purpose.
The protocol nonsense could have been avoided even more easily had Teresa May accepted the EU’s offer to leave the entire UK in the customs union, even though out of the EU and its single market - an arrangement which appears to work, problem-free, with eg Turkey. But the offer was rejected on the grounds that it would be a permanent obstacle to the Holy Grail of a US/UK trade deal. Now that we have a wonderful US/UK trade deal, we’re stuck with the protocol...um....oh. Ah.