1/ It is quite easy for the google engineers to write code detecting niche edits, and they probably already have.
They can write such code and filter the most suspicious occurrences, which then have a high probability to be bought links, etc...
2/ On the other hand a blog post is a blog post, and the probability of it being a paid link is lower.
3/ They may then (or may not, no one outside google would know for sure) decrease the value of said links in niche edits.
4/ Also an edit may or may not be stronger, but the blog post will get stronger over time, as strong ultimately (everything being equal).
Conclusion: easy for google to detect niche edits.