Earlier quoted context omitted.
Having never given much thought to it, your analysis rings true to my native Texan ears. There's another usage that comes to mind, though. One might argue that "y'all" borders on a second person plural inclusive of the speaker whereas "all y'all" marks a distinction between the speaker and the others. For instance, a peeved person would be more likely to say, "All y'all can kiss my ass," as opposed to, "Y'all can kis…
> One might argue that "y'all" borders on a second person plural inclusive of the speaker So a first person plural?
Grammatical constructs can have a lot of variation between languages, and there are certainly nuances that can't be expressed in English the same way that it can be in other languages. One thing we lack is a nuanced sense of past, while other languages have baked in ways to express recent past or distant past (e.g. Bantu languages).
My proposed interpretation regarding "all y'all" is not academic, just a native feel, and I'm sure other native speakers could disagree.