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.
X-Spinner has super-advanced functions such as auto-grammar fix, for example it will correct "a apple" to "an apple," plus it can spin "I want to eat the apple, orange and banana" to "I want to eat the banana, orange and apple." We can't list all functions here, there are too many to list! - But one thing is sure, X-Spinner will give you the best rewritten article - no other spinner can do what X-Spinner does!