Except that it is disingenuous and this disingenuosity speaks volumes of those who would willingly instigate and perpetuate such lies - and let's be honest, that's what knowingly stuffing one's own words into the Buddha's (or any of the early arahants') mouth is. If something is composed by someone else, they should have the integrity and honesty to be upfront about it, and let the audience decide whether they are prepared to take it as authoratative, on its own merits, and according to their own reason. This criticism isn't exclusive to Mahayana either - Theravada is not free from such chicanery, as the above example of the Abhidhamma demonstrates.