Weapons with additional attacks

An ambiguous wording question regarding weapons like Lelith's mane of barbs and hooks. The ability on the weapon says "Each time the bearer fights, it can make 2 additional attacks with this weapon".

Does this mean I can choose to make all of Lelith's normal attacks with her penetrating blades, and then get two bonus attacks with the mane of barbs and hooks? Or does it mean I would need to allocate at least one attack to the mane of barbs and hooks to get the additional attacks?

The same logic would apply to Grotesques with their monstrous cleaver. Wyches technically have the same wording, but don't have an alternative weapon to use.

Considering how attacks work in this edition (you can now mix the weapons used to attack rather than making all the attacks with the same weapon) Lelith can do her 4 basic attacks with any weapon she is equipped with plus 1 with her penetrating blades, using their profile, plus 2 with mane of barbs and hooks, using their profile.

One of the issues tackled in this thread. Nothing in that rule says you need to allocate an attack with the hair in order to get the additional attacks. You just need to fight.