You said it works .. but you are filing a bug report?

What works is references to subroutine in not-loaded packages. Bug report against Class::Load, which refuses to load packages after such referencing (thanks that I still have "require" working).

is this good practice or is it a bug?

Exactly. I think those are more probable alternatives.

Referencing a not yet loaded module in order to trigger loading on demand might be a great practice for saving on load time and memory requirements

I am not asking about such references in general, only about \&NotYetLoadedModule::mysub(); vs sub { &NotYetLoadedModule::mysub };