That's a total lie/fabrication that perfect contrition is a "substitute" for the Sacrament of Confession, and is directly contradicted from the citation from Trent. One must intend to go to Confession at the next opportunity. There's no such thing as a "perfect contrition" that restores to a state of justification without the intention to go to Confession. Now, Trent adds the phrase about opportunity because it's not necessary to rouse a priest at 3AM to confession immediately after said "perfect contrition", but, say, the next time there are confessions scheduled. But Trent clearly teaches that there is no justification due to perfect contrition alone with the Sacrament of Confession being required, saltem voto, at least in intention. Here's a simple case. Someone makes a perfect act of contrition, with true sorrow for one's sins because they offend God and out of love for God, but then decides he doesn't want to go to Confession, for whatever reason ... too much trouble, embarrassment, etc.
There's the Saint Jean Vianney anecdote of the grieving widow of the man who jumped off a bridge to his death. The good
Curé d'Ars told her that the husband had managed a perfect contrition in the split second before drowning. His very last sin by definition gave no opportunity for Confession.
Yet that case seems to speak more to the virtue of
hope (as a unique and sudden example of final perseverance) than to perfect contrition as a generalizable fallback for any except the most unusual situations. (Or imagine a seemingly comatose apostate unable to communicate his final wishes but lucid enough interiorly to desire repentance sincerely for all the right reasons other than fear of damnation.)
Possible perhaps with God's mercy, but to lasso outliers and attempt to construct an entire teaching around these without the necessary qualifiers? Saint Jean Vianney had the rare grace of being able to read souls. The rest of us don't.