The person you responded quite clearly stated it was an approximation to other trade situations. Your response reads as a little disingenuous given the text above, but if it was genuine the "trade" is the provision of services for the exchange of money with Chinese-owned apps. Providing software services like any other service, and indeed like physical goods, is trade all the same.

Tariff may not have been a perfectly analogous choice, but prohibition can also be seen economically as an infinite tariff. China has put bans (infinite tariffs) on a great many US and other foreign companies' services and this is some, comparatively small, reciprocation.