Just out of curiosty: how much are these Spontanmikkellers over at your end of the globe? That Spontanbasil was 15€ for a 750ml bottle, but I reckon it's actually a blend with Lindemans lambic, and hence not just any Mikkeller Spontan.I thought I had read somewhere that he uses Girardin as his base lambic. I definitely get that funky Girardin Brett note on the nose with some of the beers in this series, but not all of them.
The SpontanSeaBuckthorn is an interesting one. There isn't much of a berry or fruit flavor/aroma on top of the usual lambic notes. But there is a sharp malic acid sourness on the middle of the tongue and some lingering tannic astringency. The lactic acidity seems towards the low side. The end result is tartness up front that drops off quickly and is balanced on the finish by the tannins. The acidity is more like Sour Patch Kids or Warheads (but not as strong as the latter), rather than lactic.
I think there were two ways to go with the Sea Buckthorn. The first is what Mikkeler has done here - back off on the lactic to keep the combo of malic and lactic from overpowering the palate. That leads to a better balance, but the acidity is dropping off a bit too quick. It's a little too tart up front and not tart enough on the back end.
The second way would be to go full throttle on the acidity, in the range of something like La Folie. I think the acidity would be a bit bracing at first, but the tannins would cut through and give some balance through the finish. At least that's my armchair quarterback take on it.