I haven't used wildcard LE certs yet, but from what I know those only need a TXT record under one name. What you describe applies when you want a certificate th

I haven't used wildcard LE certs yet, but from what I know those only need a TXT record under one name. What you describe applies when you want a certificate that lists multiple explicit names, then each name gets validated individually, and so you need one TXT record per name to be validated (though you can still point all the CNAMEs to the same TXT record name, as long as they aren't used for concurrent validation).