I was under the impression that a mix of sail and non-sail boats would be ok, given the previous reception. We have the scout ship as a somewhat faithful recreation of the hjortspring boat, and the fishing ship uses oars instead of a sail. For the merchant ship, it makes sense that sails would supplement trade vessels. As for the arrow ship, it needed a bit more distinguishment from the hjortspring boat, otherwise the ships would be difficult to distinguish quickly.
I think there is a degree of plausibility in the use of sail which we can justifiably represent, while keeping a sort of replica of the real hjortspring boat for history enthusiasts to appreciate. Rock art shows a diversity of hjortspring-style boats, some complete with masts and/or sails, plenty of ship settings have single rocks denoting a mast, and north <-> south trade existed.