Here's the test: is a spell capable of targeting more than one creature? If yes, the spell can't be twinned. https://t.co/AWBo4AaLOk

— Jeremy Crawford (@JeremyECrawford) June 11, 2015

@BrailSaysThunderwave doesnt call things Targets, Find Steed + Thunderwave = good to go?
Nope. See the PH (p. 203) for the distinction between "only you" and an effect originating from you.

— Jeremy Crawford (@JeremyECrawford) June 17, 2015