Yep, in this scenario you would be able to issue a new cert every day indefinitely, and renew them all indefinitely.
If the rate limit is 20 new domains per week, is that really 20 new combinations of domains? I.e., can we request a SAN SSL for 99 domains all at once in the same request? And if so, can we then request 19 more SANs in the same week?
Note this is 20 certificates per single domain per week.