Hmmm. I tested this works:
post_hook = cat test.conf test.conf > test2.test && service nginx reload && echo test12-22
Also these work.
post_hook = 'cat test.conf test.conf > test2.test && service nginx reload && echo test12-22'
post_hook = "cat test.conf test.conf > test2.test && service nginx reload && echo test12-22"
Might Certbot remove the quotes during parse before issuing command?