You may want to read this -
Once a Saint, Always a Saint? Kind Of -- Unless You're Demoted
It was your own pope and his advisors who decided that there was little to no historical basis for 93 saints.
So first off, that doesn't say they declared anyone non-existent (let alone "officially"), contrary to your claim. Indeed, the article notes:
But they weren’t actually de-sainted, just downgraded, said Christopher Bellito, a history professor at Kean University.
"The purpose was to clean up a crowded liturgical calendar,” he said. "They decided to remove particular feast days of those saints whose origins were shrouded in more mystery than manuscripts."
So all that was done was his feast day was removed from the calendar. That's it. That's not an "official" declaration he didn't exist. Plenty of people declared saints aren't on the calendar.
Now, the article does go on to talk specifically about Christopher. Let's see what it says:
Among Catholicism’s most popular saints, Christopher was listed as a martyr.
Legend had it he carried a child who grew increasingly heavy across a river -- the child was supposed to be carrying the weight of God.
But there wasn’t enough historical evidence the man ever existed, so Pope Paul VI dropped him.
Note, yet again, there is no mention of any "official" declaration he did not exist, which is what you claimed. All it says is that he was removed because there wasn't enough historical evidence he existed, which is a very different claim.
However, even that more moderate claim seems to be inaccurate. Looking into it, this seems to be the "official" announcement regarding the changes in the calendar that happened:
The liturgical calendar of the Catholic Church as reformed after the Second Vatican Council.The first part of the book is a description of the calendar; the...
archive.org
Memoria S. Christophori, anno circiter 1550 in Calendario romano ascripta, Calendariis particularibus relinquitur: quamvis Acta S. Christophori fabulosa sint, antiqua inveniuntur monumenta eius venerationis; attamen cultus huius Sancti non pertinet ad traditionem romanam
Which means, at least according to an automated translation (they've gotten a lot better with Latin to English computer translations):
"The memory of St. Christopher, recorded in the Roman calendar about 1550, is left to particular calendars: although the Acts of St. Christopher are legendary, ancient monuments of his veneration are found; however, the cult of this Saint does not belong to the Roman tradition"
So what does it say? Well, it was taken from the Roman Calendar (that is, the calendar of the church as a whole) but is left to local ones. It notes the Acts of St. Christopher (a later document) is legendary, but that there are ancient monuments of his veneration. Its concluding statement, which appears to be the reason he was removed, is that he does not belong to the Roman tradition (he was, after all, only added to the calendar in 1550).
So not only does it not make any official proclamation he didn't exist, it does not state his existence is doubtful, just a particular later document about him was legendary. Maybe one could read that as saying we don't really know anything about his life, but that's a far cry from expressing doubts on his existence, let alone making any official declaration he didn't exist. And finally, the apparent reason for him being dropped isn't due to doubt of his existence, but his late inclusion.
Indeed, he still seems to be listed in the Roman Martyrology (a list of saints, martyrs, and those declared blessed) at least as of 2004 (I'm not sure if there are any newer editions):
The updated Latin edition (2004) of the Martyrologium Romanum as reformed after the Second Vatican Council.Contains over 7,000 saints and blesseds currently...
archive.org
I believe he is the "Christophorus, m. Lycia, 25 iul. 2 (s. inc.)"
So he does not seem to have ever been declared (officially or otherwise) to be nonexistent by the Catholic Church, and is still regarded as a saint. All they did was drop him from the Roman liturgical calendar to try to lower the number of people on it (local areas can still include him), and the "official" reason given seems to--contrary to what the article claimed--more be that he just wasn't part of the Roman tradition.