S4R - fine on idle but not when opened up

Just got this S4R, it’s running termis of the bladder, pretty standard 6k on the clock usual wear and tear.

I just came back from the workshop where the mechanic who was about to compete the belt service has given me possible some very bad news.

When you open up the throttle at the top end the bike does make a typically louder noise than usual, no banging or clanking but a deeper note as it rev’s.

He said engine - f#^**d which obviously is terrible to hear. But to be honest when I first heard it sounded fine and my initial thoughts were it’s just a loud twin as usual.

I know it’s not a lot to go on, I’m pretty stressed about it so looking for anyone to give some guidance (PS the seller is been very cool about it and we are talking)