what’s the point of the frege-geach problem if non cognitivst theories aren’t truth apt?

I’ve been reading on the frege-geach problem and feel like i finally am getting a good grasp on it, though some examples don’t really make sense to me.

here is an example i read about with emotivism

P1: murder is wrong (expression of emotion)

P2: if murder is wrong, it is wrong to murder my brother

C: it is wrong to murder my brother.

P2 is an equivocation because someone can seemingly assert it without expressing an emotion.

i understand that this statement fails because of equivocation under emotivism, but what’s the point of going that far? why can’t we just say “if (it is true) murder is wrong” is incomprehensible under emotivism because “murder is wrong” isn’t even capable of being truth apt?

why do we have to point out that embedding the statement in a conditional seems to change its meaning, making it invalid, rather than pointing out that that it’s invalid specifically because it’s not truth apt anyway?

what am i missing?