Source: every time I have ever seen "this reads just like canon!" In a comment or rec over the last 22 years
I've always assumed those comments were the result of a fic occupying the overlapping space in a Venn diagram whose circles are "This fic is good," and "This fic's style is similar to canon." After all, if a fic is good but isn't stylistically similar to the book, it would feel a bit weird to comment, "This reads nothing like canon!" But that doesn't mean that good but stylistically different-from-canon fics don't exist.
Re: DNW Workshop
I've always assumed those comments were the result of a fic occupying the overlapping space in a Venn diagram whose circles are "This fic is good," and "This fic's style is similar to canon." After all, if a fic is good but isn't stylistically similar to the book, it would feel a bit weird to comment, "This reads nothing like canon!" But that doesn't mean that good but stylistically different-from-canon fics don't exist.