Watching orb's stream I just realized that Protoss can apparently create hallucinations of units they can't build yet... but checking liquipedia there are some units they can't hallucinate at all. To this point I had just assumed it worked just like the BW spell. Are there particular strategic reasons for the change, or is it just something that changed just to change?
The only thing that occurs to me right away... is that this makes scouting easier for Protoss than it "ought" to be since you can create hallucinated phoenixes when you have no stargate. Which just seems weird.