It is a 12 minute connection at Myrdal (so unless the train from Oslo is very late) the Flam train should leave on time. Then the train has 3 minutes recovery time between Lunden (what you might call Flam Village station) and Flam- it is timetabled to take 6 minutes, when it only takes 3, if that.
With the last 4 stops (including Lunden) being request stops the train should be early if anything, assuming the request stops are not required by locals or (unusually) tourists. The chance of all 4 stations being required has to be effectively zero.
There is a reasonable chance of arriving at about 2022.
Try and be at the front end of the train, which is due to arrive at Platform 4, walk off the end of the platform, turn left (with the Visitor Centre straight in front of you) and the signposted stop is on your right, opposite a bus parking lot.
So it's two ways of describing the same place.
The bus is deliberately running in connection with that train, so it really should wait if the train is a bit late for some reason.
I suppose if really worried you could contact Norways Best, and ask for a hold on the bus, if required, but I don't see the need, personally.