Since "* remove kernel" appears to be inspecific, removing
all kernels isn't what I'd expect. It's not how mv or cp or
anything else would work.
So why not turn this around. In case somebody is doing "dnf remove
kernel" and dnf will figures out that there is more packages, then
it should fail and ask user to be more specific. That way dnf could
behave consistently and user would have to go with "dnf remove
kernel*" to explicitly specify, that (s)he wants to remove all
kernels.