How badly did they mess with Pius X's catechism? Jeepers.
So, if you read up on it -- there's an article in an old "The Angelus" by one of the Fr. Duvergers (can't recall) where he says it's a misnomer to call the 1912 Catechism the "Catechism of St. Pius X". What he actually did was to take an only one from the 1700s for the Diocese of Piedmont ... and he set up a commission to revise it, so it was not an expansion of the little one that he himself hard personally written, even though that's the popular misconception. But, that on there has one question about BoD, allegedly, whereas other editions have two or three. There's one which says that people who have the right dispositions are "on the WAY of salvation", but doesn't say they would be saved if they died on the way. But, even with the 1912 one, if you dig around, and I've dispatched various AI tools to go hunting for it, you can't actually find one from 1912. You have these "reprints" from the 1950sa, 1930s, and the earliest one that I could find was from 1920. They're labeled reprints, but you can find changes being snuck into them.
Now, there was a poster here some years ago who did manage to locate a copy put up by some museum in Italy where they were the purported originals, and there were photos of the contents ... and that version conspiculously lacked the BoD passage.
Basically, when St. Pius X died, they couldn't get rid of him fast enough. He was despised by all the Modernists, and there were many. His body was still warm when his successor had already dissolved the
Sodalitium, which had been absolution essential, and they railroaded Cardinal Merry del Val ... and got rid of all St. Pius X's "chosen" post haste.