Interesting, I just saw the Shukei piece
you referenced in your OP on Artistic Nippon. It seems he is suggesting
to use as a teapot and priced accordingly. Before buying I’d ask if when wet it has smell of clay, it could take a while to cure before use. Personally I wouldn’t want to use for tea only for water, it will be absorbent, taste like clay, and stain, but hey maybe it can work eventually for tea once it’s marinated
As white teapots tend to stain faster than darker teapots, it is recommended that you slow down this process by soaking your teapot in clean, cold water before every use.
I have a light beige fine clay mogake set by Chitoshi Morita
(Koudou Studio kiln). It has a very light glaze partly on the outside though, and does not stain with use. Inside it is unglazed and hasn’t stained with green tea.
A few TF members have Yamada Sou’s Aoyu (blue glazed) kyusu, those are unglazed white/beige clay inside, wonder how easily those stain. But I think the clay is very different from the Shukei you referenced. The Shukei clay is like my Japanese white clay kettle