That's one good reason for using bitcoin core 0.12 code as a base for development ideas. The other is the fact that segwit has not been activated and may never be.

So lets say someone spots a good opportunity for a code optimisation that does not affect the existing protocol of nodes. It can peer reviewed by more people. It can be integrated into other nodes such as core/classic/xt/bu easier by the developers who understand the differences from that code base.