As for shipping times - yes, Chinese New Year is an annual event where things just stop for a week or two.
Aside from that, however, the logistics involved in shops getting stock is a little different to small freight, especially postal services. As mentioned above, a lot of that stuff will fly wheres that path just won't work for 16 containers of toilet paper or whatever.
I had some things come from China mid last year - and they actually got to me quicker than I expected. Outside of Chinese New Year I would say 3 weeks sounds a little optimistic, but not impossible. With CNY, however, I'd add another week or two to my expectations - but I'd secretly hope for a pleasant surprise.