Yes, that's right. All crew are trained on the 350 but they have a smaller contingent trained for the B777 and A380. Being older aircraft, most of the crew have been trained on these fleets for many years, so there's a much higher likelihood of senior crew too. And being a smaller pool, there's a greater chance that they know one another. Nowadays, the A350 is the training ground for new crew too, so a lot of crew attention will most likely be devoted to training activities. You're more likely to get a green crew (not referring to the colour of the kebaya).
One of the other complications of the A350 is its galley layout which is not conducive to good service. On the MH, all 40 J passengers are served from the fwd galley which is too small: it's insufficient for plating main courses as well as storing the second refreshment service. Coming from the forward galley also means there are more roadblocks than a central mid galley, though the long-haul variant has this.
I gather it is a point of consternation between the cabin crew and management. Ask any crew onboard and they will tell you that the A350 is their least favourite to work aboard in the fleet.