Sure, that’s true, but the interesting application of the question arises with respect to how we should act. How intensely should Catholics pray for others’ salvation? The answer to that turns on the inevitability of damnation.
Perhaps you should revisit whether your assumption of the person’s being in hell at all is a foregone conclusion. It’s a nuanced question with no known answer because we don’t know the mechanism of God’s mercy and judgment in our final moments, and the lead up.
If you believe in the omnipotence of God and the infinite grace of His self-sacrifice, why should you a priori assume that God’s infinite sacrifice is insufficient to make amends for finite human transgressions? Does God not have the power to save all souls? Of course He has! The Church outlines the theoretical moral conditions in which banishment to hell occurs, which you have accurately stated, but we don’t know whether being sent to hell ever actually occurs for human souls.
Given the logical possibility that there could be no human souls in hell ever, the irreversibility of hell could be rendered moot.
From a practical standpoint, if we know that any given soul could tilt from being damned to saved by one prayer or sacrifice on our part, applied through the lens of God’s perfect mercy, how much more motivated we should be to suffer for one another! That’s a REALLY powerful insight, and it dramatically changes the messaging we should take when discussing the topic. It shifts our role from a fatalistic resignation to damnation to an empowered position where we should sacrifice everything and devote every second of our lives to others! I don’t mean we should abandon all practicality and absolve ourselves of material responsibilities, but rather that all our worldly efforts can become priceless spiritual offerings.