Hmm, only my /e/ devices (1.8.1 q & r, mata & T2e emerald respectively) have entries in the Emergency alert history but they are all clear and readable.
When tapped on they show the original alert dialogs (severe winter storm in Southern California? Global warming? More like next ice age. 
)
Unfamiliar with the decoding issues. Today is the first time I ever checked that area. My devices are either good to go or display nothing.
EDIT: Just noticed there’s a thread about this or similar subject here…