But that's similar to what I experienced in Seattle, except they say "y'all" too to be gender-inclusive now. You can spot a WA state accent by the way the say "bag" though (sounds like "beg"). My favorite give-aways for southern without accent though is saying "might could".
The infamous "northwest vowel shift"! I do this too (grew up in the suburbs of Portland) and it's common from Oregon up into BC. Didn't realize it was different until I moved to the midwest for undergrad.
I did have a hard time in the Deep South, especially the way they would say things like ve-hi-cle and such.
My question for you, is do you notice it when eastern WA people say it? Does it stand out to your ear? If not it's possible that you're just used to hearing it either way and not attuned to the difference. I'm like that when people say "pen" and "pin" differently, I can't hear a difference at all. But the "bag" thing stands out a lot since it's different to me.