Prof. Yedidya Alter Dinri records in his Hakhmei Ashkenaz B'Shilhi Y'mei HaBeynayim (pp. 278-9) as cited by R. Yisrael Peles in Yeshurun (20 p. 890) that many Aharonim held that Likkutei Maharil (aka Sefer Maharil) is not a fully reliable work. For example, the Yad Malakhi (klalei HaPoskim: Klalei Shaar HaMehabrim V'HaMefarshim: 33) cites R. Sh'muel Bachrach (Hut Hashani 31) as writing that it is pointless to make inferences from the work, given that it presents indirect information anyway.
Additionally, Maharshal writes (Responsum #7) critically about one of the hagahot (marginalia) printed in the work, first published in his lifetime, indicating that that they were unreliable. For another textual issue with the work, particularly its hagahot, see Shu"t Bah HaHadashot (9-10).
Furthermore, the Taz (OH 629:2) writes about a point in the Sefer Maharil itself:
והכותב ספר מהרי"ל טעה בזה
The one who wrote Sefer Maharil erred with this.
His roundabout reference to the one who authored the book of Maharil, seems to indicates a scepticism that it actually accurately reflects Maharil's teachings.
The Aderet writes even more sharply: that the compiler was a simpleton who made many mistakes due to his ignorance (Yeshurun Vol. IX p. 638, cited here):
שהמלקט היה איש פשוט ולא ידע כלום...לא ידע להבחין הדברים מאומה וכמו שהראתי בכמה מקומות בס"ד שס' לקוטי מהרי"ל הוא מלא שגיאות בכל דבריו
The compiler was a simpleton who knew nothing...he did not know how to understand [the activities he observed] at all, as I demonstrated in several places with the help of God that the book Likkutei Maharil is full of mistakes in all its statements.
Hattam Sofer (Pesahim 51 cited here) similarly writes that the compiler erred frequently and misunderstood Maharil.
Indeed, Maharil's own son, R. Shimon, takes issue with various practices attributed to his father! See a discussion of this in the aforementioned article in Yeshurun. This was likely R. Weiss's intent. Perhaps he was especially critical of the work as a whole, given that he perceived this particular idea as being radical.