Say they do break a bottle. After you file a claim they have to come and collect the broken pieces, the shipping container, and ALL of the original content (that's right, even the surviving bottles). Good luck ever getting the content back, even if the claim goes through (speaking from personal experience here (not with wine)).
If you said "Yes" to "Liquid, Fragile, or Perishable" they wouldn't have insured it anyway. So since you called it a "plant extract" they wont honor the insurance once they see what was inside.
Make sense?
Self insure by packing very well. Assume the box will get tossed and dropped. Pack accordingly.
I think that most wineries that do direct-to-customer sales do not use shipping company insurance either. At least non of the ones I have spoken with.
-Jeff