The point could be:
- collect bleach from apartment
- lie and claim you’ve analyzed it and it’s a perfect match
- get suspects to admit their role
Well, yeah, but whether they lie about doing it, or actually do it, it still means there is a point to getting the bleach. That was the question people have kept asking.
Taht said, simply confirming he had bleach, despite being weak evidence by itself, would still be a reason I guess.