One thing to consider - does admitting you are a dev or whatever for a particular game make the answer any better or any more correct?
Likely it doesn't. Likely the only thing that matters is the specific information that you are giving - if it is correct in and of itself, then it should be able to stand on its own as a good and thus community rewarded answer. If the only thing that convinces people of the correctness of the information is the name attached to it, then the answer is likely problematic, as there should be no need to be like "I am a dev wooo" in order to create good, factual, and likely testable/confirmable results of applying whatever answer is given to whatever game is being asked about.
So how do we solve this? Thank people very nicely for their time, but perhaps edit out the whole "look I did this thing whee I am a powerful person with title x" bits.
Admittedly, that does not take the self-promotion aspect into account.
So, let's look at the spirit of that, rather than the wording. Yeah, theoretically, according to a strict interpretation of the rule as worded, you need to tell us each and every time you post an answer/question related to something you have created. But, I hear you saying, doesn't that make your claim that we should just edit out "I am a dev yay" mentions?
It might, if we were taking this idea of self-promotion 100% literally 100% of the time.
Here's the thing, though.
I might very well have been involved on that project you are asking about, and thus, I might very well know the answer.
Take Stack Overflow for example. I know there are people there who have done things that are well known (I am not a programmer so I suck at examples), but they don't have to shout it from the hills.
As you said, things that are only answerable by devs are things we don't want, so the fact that they are devs shouldn't matter.