Pointing to a CNAME isn't legal, but it should be. This particular limitation never made any sense to me and it should be lifted.
Having a dynamic IPv4 address with multiple domains on it, updating every record would take more time.
Admittedly, I could also have a copy of the IP per domain, but the CNAME was easier to setup.
Meanwhile you can use ALIAS record and get the same result, without others noticing.
See: https://en.wikipedia.org/wiki/CNAME_record#ANAME_record