I'd be surprised if the Type-55 VLS cells aren't slanted, which would definitely allow for multiple missiles from the same bank to be cold-launched simultaneously. In fact, couldn't the VLS slant in 4 directions, therefore allowing 4 missiles to be cold launched simultaneously?
Also, the capacity of an X-Band AESA to provide guidance for "hundreds" of missiles is not an overstatement.
The specifications for the Thales Netherlands APAR reflects the fact that European navies don't need to provide terminal guidance to hundreds of SAMs. So it's just a question of dedicating processing power and TR modules to the task.
And with the proposed Chinese arsenal ship, there presumably would be a requirement for a Type-55 to guide hundreds of SAMs at the same time.
