Smetana is not simply sour cream, it is a specifically Eastern European product
It exists as a word in English too and should be accepted as a correct translation
Can't you say smetana in english? Does it have to be sour cream?
When chatting with my Ukrainian friend (in English) we always call сметана "smetana" and never call бутерброд a "sandwich". These are specifically Eastern European products which don't directly correspond to sour cream and sandwiches.
I wrote "smetana" but it's marked wrong. It's a mistake. Perhaps they'll also insist that we invent an English word for водка. Maybe they could start by using a proper Slavic word for вебдизайн.