It's not unprecedented in human history, and it's not based on economics. It's based in epidemiology and due regard for human life.
But now that you mention it, there is a reasonable economic rationale. Runaway pandemics appear to be more destructive than non-medical countermeasures.
http://news.mit.edu/2020/pandemic-he...-recovery-0401
https://papers.ssrn.com/sol3/papers....act_id=3561560
As to your feeling that my question to CC about Keynesian economics is misplaced, I don't think it is. Increased government spending is one of the few effective tools against a demand shock, to avert or mitigate a debt-deflation spiral.