I got 3 'guest posts' as a review copy.
Report was delivered in 15 days. Stats of the websites are as advertised and indexed.
Articles were 'okish'. Some parts were not accurate. On the 3 posts the article was re-written or spinned, as it was pretty similar.
What I don't like is that these don't look like legit sites. Here is why:
1) All websites were previously used for different purposes (cpa, business, insurance, foreign sites, seo); some were used multiple times for different niches according to webarchive. If this is a coincidence, than all these 3 bloggers got themselves expired domains.
2) There is no traffic on them according to semrush. 2 of the websites rank for 1 obscure keyword between 50-100. 1 website is ranking for about 5 keywords on +40 and it is decreasing in ranking. On the other hand, MOZ is showing that all 3 websites are not ranking for any keyword.
3) No social profiles. All websites had the logos for facebook, twitter, but all where linking to the facebook.com or twitter.com. Even searching for the domains on facebook, I got only one page for one of the websites that is inactive since 2014, when it was a different website.
4) No traffic. Although the posts are made on 28, 29, 30 May, I got no traffic from any of them. I see others are stating that they got some traffic. Maybe they are in a different niche and got posts on active website with a different type of articles.
Maybe any of this points can be exceptions, but as these 'exceptions' are 4 I am thinking that this are PBNs.