Its clueless to issue "verbal warnings" when there are no consequences that the manager is willing to follow through on beyond those warnings. And clueless, as seems to be the case here, to use "verbal warnings" in place of, rather than alongside or in response to failure of, efforts to diagnose and resolve problems with an otherwise brilliant employee that apparently the company is so dependent on that firing him, in the manager's eyes, literally is not an option.

So, regardless of the reasonableness of the expectation of timeliness, yes, the manager here seems rather clueless, from their own presentation of the situation.