Come to think about it… That doesn’t work on port 443 for google.com either. It does however work with the -Tflag (TCP ACKs on), so maybe it just can’t/won’t do ICMP over SSL? With -T I can successfully traceroute acme-v01.api.letsencrypt.org -p 443 -T.
EDIT: or just plain traceroute acme-v01.api.letsencrypt.org 443 works.