Perhaps they mean: assuming one already has legal authority to access somebody else's app data, this is a legal mechanism to remove any remaining technical barriers? (I.e., the other mechanism available for getting past technical barriers would be illegal, e.g. torturing someone who knows the password.)

Just guessing, and trying to be charitable.

They only sell it to government agencies so they assume that any use for it would be legal even if it’s not.

There were reports of Mexican cartels having access to cellphone decryption software. Yeah, you can say that the cartels are the government in those areas where they have the power. That tells you everything you need to know about lawful access.

Yeah I agree. This type of solutions can always end in the wrong hands.. But you don't need to go that far. The same agencies that buy it can use it in an unlawful way.

They also didn't rule out non-lawful access ;)