When a claim on Wikipedia includes a citation, you should always try to locate of copy of the cited work if you are looking for further details about that claim.
In this case, the source cited is The library : an illustrated history, by Stuart Murray. Fortunately for us, this is available to borrow on Archive.org.
The passage you quote is taken directly from the book, although without the supporting explanation:
One significant effect of typesetting was that authorship of works could be spotted more easily, making it difficult for copiers who have not gained permission. Previously, texts were often copied and recopied, without attribution, into other works. This obscured the original authorship. Identical typeset editions, however, bore the author's name and were printed by the thousand - establishing for posterity the original author.
There were therefore many more copies of a given work in circulation, each of which carried the author's name. This made spotting plagiarism much easier.