Here we go.
So on what basis are you suggesting astringency, is it personal experience ? Or just something you read somewhere and decided it would be your very own fun fact to regurgitate at will?
Remember, I don't advocate a coffee-grinder crack, for other reasons than yours, but the person doing this reports no such astringency issues. Is actual experience from another brewer not enough for you to accept that your theoretical musings may be off the mark? Or are there deeper ramifications being shot out willy-nilly between the lines, in that he truly is getting astringency issues but is too inexperinced a beer taster to recognise them ? For those who have previously stated astringency in coffee grinder cracks AS FACT, how many have actually brewed a full batch with this method to confirm it?