Is Grammarly a Keylogger

I read this post by Michael Tsai - Blog - Is Grammarly a Keylogger? and I found it concerning since I do use Grammarly.

Should I be concerned enough to stop using Grammarly? @MacSparky I would like to hear from you since I know that you use Grammarly.

Interesting.

From the article:

This is completely unsurprising for a server-based product.

Well, only kind of. It should be possible for content to be sent for processing on the server in such a way that their team does not have easy access to it. And it should only be retained for the amount of time that it takes to process it (or, perhaps, for a session if it’s not efficient to send entire documents each time.)

Maybe I’m missing something amazing about Grammarly’s AI… but why does checking grammar need to be cloud based? (I appreciate some specific features, like plagiarism detection would need to be).