It's been commented that the A350 is no longer suitable for MAN, as the B77W now seems to be the right sized aircraft for above and below deck.
What's worth noting is that the next A359 destinations are direct B77W replacements with no frequency increase, so, a loss of capacity on those routes.
The fact CX feel the need to keep the B77W on the route should be seen as a positive, not a negative.