Aircraft on MMB = 340-600 but on new booking = 747?

Just received an email from VS notifying me that my VS23 LHR-LAX flight in May is cancelled and we're rebooked on VS7. Great I thought as prefer UC on the 747. Checked seat map on MMB and see that the VS7 is an A340-600. No big deal. As what seems to be routine (from reading other posts) my travel party was all split up, so I regrouped us back together in pretty much the original seats we had on the VS23......goodness only knows by VS choose to split up a party of four! Anyway, then out of interest I tried to book the same flight. Sure enough the VS23 is no longer showing for that date but the VS7 shows as a 747? I'm assuming the seat map is more likely to be correct ?|

I think the seat maps on "my booking" are more up to date. Sounds like similar situation as my flight to BOS, showing as a A340-300 under flight information but as a A340-600 when checking the seat map on my booking.