Discussion of False Attrbution in Don Quixote?

I was reading the author's preface to Cervantes' Don Quixote, and I saw the following interesting exchange:

[T]here came in unexpectedly a certain lively, clever friend of mine, who, seeing me so deep in thought, asked the reason; to which I, making no mystery of it, answered that I was thinking of the Preface I had to make for the story of "Don Quixote," which so troubled me that I had a mind not to make any at all, nor even publish the achievements of so noble a knight.

...

Also my book must do without sonnets at the beginning, at least sonnets whose authors are dukes, marquises, counts, bishops, ladies, or famous poets. Though if I were to ask two or three obliging friends, I know they would give me them, and such as the productions of those that have the highest reputation in our Spain could not equal.

...

To which he made answer, "Your first difficulty about the sonnets, epigrams, or complimentary verses which you want for the beginning, and which ought to be by persons of importance and rank, can be removed if you yourself take a little trouble to make them; you can afterwards baptise them, and put any name you like to them, fathering them on Prester John of the Indies or the Emperor of Trebizond, who, to my knowledge, were said to have been famous poets: and even if they were not, and any pedants or bachelors should attack you and question the fact, never care two maravedis for that, for even if they prove a lie against you they cannot cut off the hand you wrote it with.

I wonder if this was indeed occasional practice. Cervantes did follow through on this "friend's" advice -- he has "some commendatory verses" by "Urganda the Unknown," "Amadis of Gaul," Don Belianis of Greece, attributed to fictional characters from the genre.