They're basically recommending changing verifiable references that can easily be cross-checked and verified, to "printed on paper" sources that could likely never be verified by any other Wikipedian, and can easily be used to provide a falsification and bias that could go unnoticed for extended periods of time.
Honestly, that's all you need to know about Wikipedia.
The "altered" allegation is also disingenuous. The reason archive.org never works, is precisely because it doesn't alter the pages enough. There's no evidence that archive.today has altered any actual main content they've archived; altering the hidden fields, usernames and paywalls, as well as random presentation elements to make the page look properly, doesn't really count as "altered" in my book, yet that's precisely what the allegation amounts to.