That the dynamic address list entries are tied to the TTL and automagically update once the timeout elapse is not clearly documented in the manual but is something you can observe when adding sub domains with short TTL and changing IPs, usually those pointing to hosts from CDNs.
And the change item above shows that the TTL was really used, and not some fixed interval of 5 minutes that coincidentally matches the timeout of the tested domains 
As for manual renewal of certificates created with add-acme, I also complained about the missing option to manually trigger it in the 7.22 release/rc thread, as add-acme only creates new entries and errors out if you specify the same name as existing entry instead of renewing it. Currently my script that attempts the renewal (and also handles toggling the firewall port and www) just creates new ACME certs with the name sub.domain.name@unix-timestamp, so that the name is guaranteed to be different from the name of the existing issued certificate.
Once that succeeds (script needs to periodically poll the value of acme-status because add-acme runs asynchronously in the background), the new certificate is set for the router services that use it (www-ssl, SSTP, User Manager, as well as being exported for unbound DoT in container). Only then is the old certificate removed (by searching for certificates with the acme-managed flag, same domain-names as the new certificate but with different fingerprint). It's safer that way because it prevents the old certificate from being removed in case there are problems with issuing the new one. Also it prevents the certificate being from removed while still being referenced by or the settings (such as www-ssl or SSTP, etc...).
This is normally not a problem. For example, when testing my scripts I could reissue certificates for the same domain within a few minutes with Let's Encrypt. Let's Encrypt documents all that here:
https://letsencrypt.org/docs/rate-limits/
For the exact same subdomain, with Let's Encrypt, you can issue the certificate 5 times within 7 days. When that limit is up, just wait for 34 hours and you can reissue a new one for the exact same domain.
So I assume the other vendors probably have similar limits that are not too restricted.