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That paragraph is not the journalist's writing, it's a quote, presumably transcribed from a verbal interview.

How is this an excuse to spell "grisly" as "grizzly"?

TIL, at 41.

Mice are quite grizzly, though.

Yes, which means the journalist who transcribed the interview chose the wrong homophone for this particular word.

“itsy bitsy” stories don’t generate clicks

It's known as "The Grauniad" for a reason.