Hi,
I do not know why they say "unordered", as a LUW can require a certain order of operations. While there may be a feature now or in future that could paralellise the operations, it should not do so within a LUW.
I am pretty certain from my own observations that the payload is deserialised so that the operations occur in the order provided. Doing it another way would actually be harder to implement in the GW engine. If that's not the case, you'll soon find out. Experiment! 
Ron.