The Bio flails abilities text reads
Each time the barer fights, you make a number of hit rolls against the target unit equal to the number of models from that unit within 2" of the Stone Crusher Carnifex.
There could be a few ways to read this.
1) A Chainsward grants 1 addition attack with the chainsword "When it fights". You don't actually have to use the chainsword to get the extra attack, there fore I feel like the bioflail just generates extra attacks regardless of whether you select it as your weapon or not. (So the SCC A characteristic + number of models within 2".)
2) each time you pick the bioflail to attack it generates a number of attacks equal to the models within 2" (Number of models within 2" of SCC x A characteristic)
Any others? What does everything think is correct?
Right now I am thinking it's 1. Many weapon abilities wouldn't do anything if you had to select the weapon for it to trigger. And if you picked the flail as your weapon it would just be 1 attack using it's profile. The ability doesn't seem to say otherwise.