Why should a foreign marketplace get the same benefit of the doubt as a domestic market? Especially if those foreign markets belong to countries that are hostile to mine?
Regular people are not someone custom wants to make an example of for ordering from a banned foreign company. Large companies will carefully check their supply chain to ensure they are not buying goods from banned companies, but tiny companies and regular people won't care as much.
I expect that the EU will have (if they don't already have) rules similar to the US and countries there will generally enforce them. However other countries (China!) will not care as much.