Having used the Sawyer inline filter, which uses the same hollow fiber technology as the Hyperflow, the dye test should not work.
If there is active charcoal in the filter, it would remove the dye color, which would show that the filter is working.
In the case of using the Sawyer inline filter, I have put green/brown water through it and it came out greenish.
The Sawyer rep that I spoke to at REI says that things at the molecular level, such as electrolyte powers, will pass through the hollow tubes/fibers, but larger things like bacteria will not.
Unfortunately, the negative to this technology is that you are working completely on faith.
If it freezes and is damaged, I don't know how you could tell unless large particles were passing through to the clean water bottle that you are drinking out of.
If the particles are coming through, something is really screwed up inside of it.