Stock samsung launcher here, if I change tracks using the widget it works perfectly fine.
Common scenario this issue occurs, song playing in the background, phone is now locked, songs have changed to something else, open up phone, look at homescreen, current song play is different from the one on the widget, tap widget to get into Poweramp, come back to home screen, widget showing correct track now.
Note, the information on the lockscreen is fine, which is why even though it's been there for over an year, it didn't ever bother me, just made me wonder what's going on in the background for it to not update itself.
I can provide logs if needed, just tell me where I should send them
Edit
I just tried the own scenario I mentioned, put the track at end so it changes by the time I have phone locked, but it updated itself when I unlocked and checked lol
Not entirely sure how to create it, but that's usually when it happens, but it didn't happen when I try to recreate it.