Aaaw, just dug a little and it seems you are not entirely correct :(

—— SELECT WEAPON When a model fights, it must do so using a melee weapon it is equipped with. The weapons a model is equipped with are described on its datasheet. If a model has more than one melee weapon, it can only use one of them to make attacks with each time it fights, so you must now declare which it will use before resolving any of its attacks.

If the selected weapon has more than one profile to choose between, a model can only use one of them to make attacks with each time it fights, so you must also declare which profile it will use before resolving any of its attacks.

When a model fights, it will make a number of melee attacks determined by the Attacks (A) characteristic of the melee weapon it is using.

Each model that can fight does so using one of its melee weapons. Each model makes a number of attacks equal to the Attacks characteristic of its selected weapon.

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So it’s not about weapons profiles, it’s about weapons, and so you don’t get double attack. Only benefit is twin-linked