Lionel has had DCC compatibility in Legacy O scale locomotives since 2013. It was introduced in American Flyer Legacy SD70's in 2012. The DCC feature is automatic with no switches to set.
Boy, that is news to me, and to Lionel as well I suspect! I think you better recheck your facts!
I know that some AF models have DCC capability, but I have yet to see it mentioned in any context for O-Gauge Legacy. I have a lot of Legacy stuff, and there's no mention of any kind of DCC capability.
The DCC capability is a function of the BEMC control board, that isn't used in O-Gauge Legacy.