Can I swap a lvl 1 Warlock spell for a lvl 5 Warlock spell?

@JeremyECrawford @mikemearls If I'm a Wiz 10 / War 1 and I gain in a level of War, can I swap a lvl 1 War spell for a lvl 5 War spell?

— Jez (@Not_Jez) May 10, 2016

When you multiclass, you determine the spells you know in a class as if it was your only class (PH, 164). #DnD https://t.co/qWdWaq4yky

— Jeremy Crawford (@JeremyECrawford) May 18, 2016