There’s a bit of documentation on these decisions in the Standard Rules:
The “first” rules in the turn sequence cover us up to the end of the events which take place in the model world during this turn’s action(s). […] We then run the scene changing rulebook, because people often write every turn rules which are predicated on particular scenes (“Every turn during the Grand Waltz: …”), and such rules will fail if we haven’t kept up with possible scene changes arising from something done in the action(s) just completed.
We now come to the rules anchored at the end, using “last”. This part of the rulebook is reserved for book-keeping which has to happen positively at the end of the turn. First, we check for scene changes again. We did this only a short while ago, but scene changes might well have arisen as a result of rules which fired during the every turn rulebook, or from timed events, or in some other way, and it’s important to start the next turn in the correct scene — so we check again to make sure.
In other words, the designers’ intent seems to have been that scenes can respond to changes in world state from actions or from every-turn rules, which are the two main ways the state can be affected.
(You may have looked at this already, but it seems useful to have in the thread for reference.)