Just guessing. I see no use for VVT in an essentially constant speed engine.With small engines about the only way to have variable timing is variable duration and that only changes the duration that valves open and stay open. Which give a responsive engine but I haven't that in anything under six cylinders personally.
Well the 1979 Chevy Malibu small block V8 I had did but it also had a 700R4 transmission installed too. I won one bet with AAMCO transmission shop when I went for fluid and filter change. The manager argued with me that I didn't have one in it as they didn't come with them. Boy lunch was plus I got a free fluid and filter change out of that.Just guessing. I see no use for VVT in an essentially constant speed engine.
I've never seen an engine that had variable duration but I have a 4 cylinder that has VVT (Acura 4 cylinder).