No, as said it is used in legal matters, example:
https://www.brocardi.it/massimario/59534.html
And you go tell this Italian professor:
http://www.diit.unict.it/users/alongheu/linguaggi/aa0910/lez...
The point is that it is actually correct in Italian, if you think about it also in "arrotondamento per difetto" (as opposed to arrotondamento per eccesso")[1] the meaning is that of "arrotondamento per mancanza", i.e. meaning #1 in the Treccani dictionary while it is much more commonly perceived as meaning #2.
[1] respectively "round down" and "round up"