This is obviously worded from Barca's perspective only:
"Lionel Messi hasn't shown up for his PCR test today in an attempt to put pressure on the club to let him leave."
Sound to me Messi's camp already entered the next level and that is
(in my words!):
I'm not a Barca player anymore, I HAVE left. Look at the burofax.
You've had your chance of negotiations, and you refused.
I will sign a City contract whenever I'm in the mood.
Go to court if you like.
If you behave now you get a second chance, maybe.
Btw, giving Barca some kind of generous symbolic compensation would only show City in a superior position giving the poor buggers a sweety. It would hurt Barca even more. They are a complete mess.