Fine. We’ll turn to the law, and put to rest this notion.
CIC Can. 960 Individual and integral confession and absolution constitute the only ordinary means by which a member of the faithful conscious of grave sin is reconciled with God and the Church. Only physical or moral impossibility excuses from confession of this type; in such a case reconciliation can be obtained by other means.
There’s that word “ordinary” again. And further, this law covers Confession. It is clear that confession must be integral. Integral means that every mortal sin of which the penitent is aware must be enumerated in kind and number, and that is to include any circumstances that change the species or gravity of the sin. And to ensure you know this definition of “integral” is not of my own making, here’s a canon lawyer right here. Google the term “integral confession” and you will find the same definition all over the place.
http://canonlawmadeeasy.com/2007/12/13/confession-and-general-absolution/
It must be individual. In other words, outside of what’s permitted by law (war, disaster, crashing plane, sinking ship), general absolution is not permitted. And then, only with the intent to go for an individual, integral confession if one survives the extraordinary circumstance.
Not even mere danger of death excuses the requirement for integral, individual confession, unless this danger now constitutes a physical or moral impossibility. The person can’t speak, death is coming in minutes (i.e. “imminent danger of death”), there is no time for the full ritual. In which case, it IS sufficient for the priest to obtain an indication of repentance before absolving. But if this danger of death is, say, due to illness, and death is foreseen, but is still a day or two away, and the penitent is conscious the ordinary law still remains and the penitent is still required to enumerate his mortal sins. This is the case because no one is bound to the impossible, and the law states as much. That’s why the law explicitly mentions physical or moral impossibility. Outside of the impossibility, canon 960 imposes the requirement of integral confession.
Your analogy with regards to the Eucharist is faulty because unlike the Eucharist, whose validity is determined only by form, matter, minister, and intent. If a suspended priest says Mass, he does so illicitly, but validly. Confession also requires the power of governance because it is a juridic act of the Church. That is to say, Church law, and not merely divine law, also is a factor in whether Confession is valid. Canon 960 makes integral confession a requirement.
So yes, unless you are on a crashing plane or choking in your own blood and will be dead in five minutes, a full enumeration of any unconfessed mortal sins is required. This is the law of the Church. And on the catechetical side, it is clear over and over, from the Baltimore Catechism onward, that intentionally concealing a mortal sin invalidates the entire confession and incurs an additional sin of sacrilege.