As far as I know, there is no papal document pertaining to gargoyles, and St. Bernard would be the first Doctor of the Church of whom I am aware that spoke on the issue—thus to the extent that the Catholic Church has an official stance on them, what you quote is it.
The Pope is lucky to get people who mostly agree with him to listen to him. If a Bishop and a Pope and a Parish priest are all in agreement, then things happen that reflect the Papal wishes. If there is some disagreement, the Papal position will in practice prevail only if one of the other two happens to agree with the Pope—and sometimes that won’t be enough.
There is a point in being reminded that evil exists. I’m not in the habit of carving or paying for gargoyles, and if I make the acquaintance of someone who is who values my advice, I’ll try to remember that St. Bernard said something—and may even remember your post.
But elevating demonic graven images on a church building is simply not the way to remind people of that, unless it is a satanic church.