Definitely getting strong uncanny valley prose vibes.
Hard to tell if it's generated or written in an attempt to be as plain English as possible, but either way feels strangely vacuous for a technical opinion piece. There's no writer's voice.
I think it's absolutely an opinion piece - defining specific items as principles by definition means expressing opinionated ideas about the relative priority of those items over others. Also, imperative mood contains value judgment, which is inherently opinion-based (e.g. "Never expose PII"). Making arguments for why you should or should not do things requires expressing opinions about relative importance, weight etc.
If this were instead an article describing what feature flags are, or one performing a survey of various approaches to building/scaling them, I think the lack of voice is just fine - that's dealing in statement of fact. But this article mandates and implores and exhorts - the value judgments inherent in that pathos are empty without genuine authorship.
Also I'm not saying the lack of voice is bad even for conveying meaning or teaching - more that it is jarring and uncanny to read imperative claims in an empty robotic voice devoid of ethos.
Finally, I also might be biased by my first documentation love, the zeromq guide, which is an extremely-strongly-opinionated piece of docs that does its job exceptionally well. I think when writing about how or why, a strong writer's voice is more compelling. This article stretches past just the what into those other question words, so its seeming lack of authorial authority falls flat to me.
