No, because the point of client-side encryption is that the service provider does not have the data to hand over.

I think the point is, if all they sent was a wiki article, they wouldn't be responding to the spirit of the subpoena. Instead they'd be expected to write up an explanation that they don't keep full data, and they would probably still be required to hand over metadata that might be useful.

And to be fair, the original commenter didn’t say that the only thing sent was the wiki article. It might be one of a dozen URLs included in the company’s reply boilerplate.