Subjectively, people don’t like it or recommend it. Objectively, it doesn’t alter anything in a way one could even accurately measure or analyze. Except maybe in high performance or exotic engines.
That's just not true. This isn't subjective at all. Actual results from actual testing say otherwise.
Even in low performance engines, chemical interaction of the additives may result in degraded performance. Not always, but may.
And you have no way of knowing that is happening in your low performance daily driver.
You really need to talk to some folks who formulate oil for a living. Different companies use different chemistries. Changing the mix of those additives can result in negative interactions.
There is a tendency on this, and other, forums to reduce chemistry to "calcium" or "phosphorus" or 'Moly" when chemistry is far more complex. The elemental (looking at elements only) analysis of a UOA, or a VOA, is like reducing computer code to letters of the alphabet.
Saying, well they're both calcium so they will work OK together is like saying, sure, that bit of code will work with this other bit code because they both have "D" in the language.
It's a ridiculous over-simplification of a complex set of interactions.
Without rigorous, complete, testing, you simply have no way of knowing if your mix will have negative interactions. It may work fine.
It may not.
But you cannot know without the testing, and wishful thinking and internet opinions won't change that.