I think everyone else, with the examples that have been given, pretty much quote everything that deserves to be quoted. The point I am driving at is that there are many many rules in 40k that offer only one method of many to go about playing. There are very few circumstances in the game where order of operations becomes important.

taking casualties

Casualties is probably the most explicit section in the book. There is a very particular way to do this, and it is immutable.
Almost everything else in the rulebook is not explicit. It is this where the movement rules are open to flexibility, and the examples given are just that, examples. For example, while you are moving individual models, you break coherency, it is just that the final position must maintain coherency. There is immense flexibility in the movement phase.