Okay. I may have been misinformed. I was told a while ago the a “Cardinal sin” was a sin you had to see a Cardinal about. It couldn’t be forgiven in the Confessional by an ordinary priest. It had to be a Cardinal, a Bishop or the Pope. For instance, the sin of abortion used to be reserved to a Bishop or higher and couldn’t be relieved by your local parish priest. That is how it was explained to me. That was years ago in the 70’s in fact.
I’ve tried to find this “cardinal sin” explanation spelled somewhere and cannot. I’ve even found references to the Capital sins actually being the Cardinal sins, in which case 1 KE you were correct. But I also know that there are sins that are Reserved to the Holy See or a particular Bishop or Office, etc. These are called Reserved. This is as much as I’ve been able to find written as well. My only conclusion so far is that the term “cardinal sins,” was actually a sort of “nic name” for them at one time and has lost its usage.
Oh well. That’s the rubber hittin’ the road. Please forgive if I’ve ruffled feathers.