Different approaches creating wildcart in docs for rhel6/rhel7/rhel8

I see in docs use different approaches for getting wildcard cert:
For centos6/rhel6-nginx - Follow Docker instructions.
For centosrhel7-nginx - manual (if DNS provider doesn’t support certbot).
For centosrhel8-nginx - again follow docker instructions.

It’s just inconsistent docs here? Or the versions have big changes, which require different approaches?
If it just inconsistency which one is preferred?

IMO, the preferred way to deal with DNS validation (and, really, most use of Let's Encrypt for any purpose) is to not use certbot at all, but rather use a client with extensive built-in DNS API support like acme.sh:

Hi @GraDea

manual is never preferred. But if the dns provider doesn't support an API, only manual is possible.

I think @GraDea question really is: why don't the docs recommend Docker for centosrhel7-nginx?

By the way, if your DNS provider doesn't have an API supported by certbot, using Docker won't help you at all.