From the June 2016 Monthly Report (emphasis mine, to the point of the issue at hand):

One such technology is the Global Serialized Variables which are designed to make the gameplay programmers’ lives easier and help optimise the network bandwidth. Previously when we were using “aspects” it is up to the gameplay programmer to decide what information needed to be sent over the network and then also to deal with both writing that information out on one end and reading it back in again at the other. This was always prone to mistakes in transmission because of the nature of network latency, which is unfortunately never really under your control. If you don’t receive, read, and parse the data in exactly the same manner you wrote it out you end up with a disconnection, which can prove more fiddly than you’d imagine. It was also very inefficient as if even one bit of data got changed the whole aspect block would have to get sent. The serialized variables takes all that away, the programmer just marks which variables they want to replicate to the server/clients and then the underlying system can just detect which have changed since the last time they were sent, and which haven’t, and takes care of the rest in a nice and efficient manner.