I have recently purchased a new duo and love it. I am concerned that the belt may be too tight as when walking beside the bike the pedals continue to turn instead of the freewheeling. Is this normal?
Sounds like you have a alloy freewheel. Yes, it’s normal. Ming makes the alloy freewheel very tight, possibly to make it more water and dust proof than the old plastic freewheel, therefore its coasting resistance is higher. While I do not enjoy this aspect of alloy freewheel, it is more efficient (at least in my experience) when it comes to forward pedaling. An acceptable trade-off in my opinion.
If it really bugs you, try replacing it with a pre-2009 plastic freewheel. Its coasting rotation is much smoother and quieter. I heard the plastic freewheels made since 2009 are tighter than before as well but still not as tight as the alloy ones.