Private message exchanges do not result as "official stance" without authorization. This is not an issue of law, but of procedure and etiquette. And yes, you can lose your professional standing - that is: your job - by disregarding it.
You infer far too much from changes in errata on a peripheral matter: a digit from stats for an effect in a complex item.
Not quite. Atlas and David changed the digit, conceding that point to you. But we also read here and here on the forum:
In other words: you think David answered that question in that private message exchange, while he does not.
So in that private exchange was a misunderstanding, how it applied to the working of ArM5 p.99 Constant Effect Devices. This happens all the time in talks and message exchanges.
But as it was you, who made part of that exchange public on this forum as "official stance" on that topic, you alone are responsible for not having detected and clarified that misunderstanding before.