ae471fa978589fb61ecb0f89bbfe4d43cf2d5eac intended to deprecate the `--keyserver` option for `gpg` way back in 2.1.9. The stated preference on the gnupg-devel mailing list is to use the `keyserver` option for dirmngr. and it's not strictly necessary today because gpg ships with a reasonable default keysever.
`gpg(1)` also explicitly says:
--keyserver name
This option is deprecated - please use the --keyserver in ‘dirm‐
ngr.conf’ instead.
As far as i'm aware, `gpg --keyserver` has never been un-deprecated, despite the fact that it overrides the keyservers preferred by any running `dirmngr`.
However, `gpg(1)` also says in four different places that this option "must be used", and `g10/keyserver.c` contains a warning message `"(use option --keyserver)"`
These latter bits at least should be cleaned up if we're serious about deprecating `gpg --keyserver`.