That’s really weird. I have tested WordAI and Spin Rewriter with Copyscape and the results were always 80%+ uniquness, even 90%+. I don’t know how u spun the content to achieve such low results, but this is definitely way too bad. As for the block spinning, I have to be honest, this is the first time I’m hearing of it and I will have to check it out when I have a bit of time, but generally, yes, in the best case scenario, you would manually touch your Tier 1 content to make it 100% human readable and as unique as possible. For lower tiers, you can do pretty much anything, but again, the better quality of content, the better results you will have. That’s in my opinion and experience.

The content above is 98% unique according to Spin Rewriter and I really like it. It actually seems better than the WordAI spin – only the “Standard” one however, it is no match for the “Turing”. One thing that the spinner failed to recognize is the “green eyes” phrase where it replaced it with “environment-friendly”. Yea, I laughed too. Anyway, here is the spintax for those interested in more testing:
Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.

4. Tier 2 content (content that is keyword rich and relevant to your niche. Doesn’t have to be all that readable, it just has to be indexable by a search engine.)– Here put same options as with the Tier 1 content situation with the only difference that you set the 1st input to “Regular.” It is important that lower tiers have a lower quality of content compared to upper tiers.