Your opening post perfectly captures the trigger for this whole discussion.
You mentioned common industry terminology. I see this constantly in backend documentation. A phrase like "implementing connection pooling to reduce latency" will be flagged, not because it's plagiarized, but because it's the standard, precise way to describe that action. It's a signal-to-noise problem where the legitimate signal is drowned out by inevitable string matches.
The key step for me is to treat the flagged result as a data point, not a verdict. It forces me to click through and examine the matched source. If it's a StackOverflow answer I wrote, a company internal wiki, or the PostgreSQL docs, I can disregard it. The tool is functioning as designed, but I'm the one adding the missing authorship context.
sub-100ms or bust
Yeah, that happens to me all the time! Just last week I was documenting a simple AWS S3 bucket setup and the checker flagged a line about setting "Block Public Access" to true. It's literally the default best practice, but I guess the phrase is everywhere now.
So I just ignore the matches that link back to my own GitHub readme files. It's a bit annoying, but I see why it happens.
Does Writesonic show you the specific source URL it's matching against? That's the first thing I look at now.
The source URL is absolutely the critical piece of data. In my experience with these checkers, the ones that don't show you the match are functionally useless for technical work. They create anxiety without providing the means to resolve it.
Your AWS S3 example is perfect. That string match is almost certainly from AWS's own documentation, a common tutorial, or your own prior work. Without the URL, you're stuck guessing.
Most of the paid services I've tested do expose the matched source. The workflow then becomes checking if it's a) your own content, b) official documentation, or c) a truly unknown third party. The first two are false positives for our purposes.
benchmark or bust
Your own example is the whole problem. These tools sell you a "plagiarism check" but what they deliver is a glorified string diff. It's a cargo cult of originality.
You said it yourself: the algorithm lacks authorship context. So why are you paying for its opinion? It's just matching fingerprints without checking who owns the hands. Flagging your own prior work as a copy is a feature, not a bug. It proves the tool is working as designed: badly.
The fix isn't in the tool, it's in your expectations. Stop letting a dumb crawler tell you what you already know.
Just my two cents.
I've only used the free version of Grammarly's checker for my blog, and it flagged my own GitHub tutorial from last month. So I'd guess it's a universal issue like you said.
That whitelist idea for paid versions sounds perfect. Has anyone actually seen a tool with that feature? It would solve the whole internal log problem.