From what I have read/seen, there's really 2 versions of these heaters, we'll call them small and large. Small (as pointed out in your graphics) are ACTUALLY 2-5kw output heaters. Large are ACTUALLY 5-8kw output heaters. The kw output depends on the settings set by the controller/LCD (low to high). I don't think you "got lucky" with the label that appeared on your unit, I think it's all related to being broken Engrish / misleading advertising / general confusion. So yours isn't really a 2kw heater, it's a 2-5kw heater. The one I have installed in my 03 T1N is likewise, a 2-5kw SMALL heater.
The small version of these heaters is definitely adequate for vans of this size, in fact I'd say they're better for vans of this size. You don't want to oversize it and go with the 5-8kw heater, as it'll likely be TOO powerful. Too powerful you say? Yes, and as a result you'll likely run it on low for most of the time, which is going to lead to more soot buildup over time which is going to lead to more maintenance needed / shorter lifespan of the heater. When you turn your heater off, it actually turns itself on HIGH for a few minutes to burn off any fuel/soot in the system (whilst turning off the fuel pump) to clean it out before shutting down for this very reason.
If you've got a T1N, the smaller 2-5kw version is the way to go. Or if you want a heater that can also pre-heat your engine via the coolant loop, these guys have also hit the market recently
https://www.alibaba.com/product-det...?spm=a2700.7724838.2017115.145.2de64ebdUUEsKb