The problem now is that (imho) 99% of the links posted on the internet are spam.
Unless you have a baseline of "what was here first" and "exactly when every website went live with what links" like Google does (because they have been indexing websites since the dawn of time as far as the internet and linking is concerned. Heck, there wasn't even backlink spamming prior to Google because Google was the first search engine to rank by number of backlinks!)... you're going to have a really tough time determining what spam is and what it isn't.
Just because a link is added to content after the content already exists doesn't immediately qualify it as spam. 99% of links being spam is a pretty massive assertion, is that anecdotal or backed by any actual data?
Even if you have had a perfect history of when links appeared you're still in the a rough ride. Furthermore, absence of the that information doesn't invalidate the author's approach (but having it might improve its effectiveness).
As an aside, you have use Ahrefs.com to get pretty decent tracking of when links appeared since it started (I think ~18 months ago or so). Given that the rate of spammy pages is increasing extremely fast and old spam pages are dying off, I imagine that in the not too distant future you'll be able to get decent link history for many sites.
Unless you have a baseline of "what was here first" and "exactly when every website went live with what links" like Google does (because they have been indexing websites since the dawn of time as far as the internet and linking is concerned. Heck, there wasn't even backlink spamming prior to Google because Google was the first search engine to rank by number of backlinks!)... you're going to have a really tough time determining what spam is and what it isn't.
Which 1% do you decide to focus in on?