ARTICULATEDS are two engines under a common boiler. Chuff rates go in and out of synchronisation in the real world - pretty difficult to do electrically.
PMF AND Throttle Up had cam driven mechanical contacts on axles to synch their chuff rates with actual wheel rotation. In today's 'whose got the lowest price world', dual independent chuff rates may be a luxury many can do without.
Certainly, if won't be in any of the cheaper units.