Sterility assurance is a process, not a claim
Lab grade bacteriostatic water is manufactured under recognised GMP frameworks with batch records, validated sterilisation and documented sterility assurance. The label is the tail end of a documented process.
Generic imports frequently arrive with none of that paperwork. The sterility claim sits on a printed label with nothing verified behind it.
pH is the quiet variable
Preserved water should sit near neutral pH, typically 4.5 to 7.0 for a preserved lab-grade product, and critically, consistent batch to batch. Some imported stock drifts alkaline, and a drift outside the expected range changes reconstitution behaviour.
Researchers chasing a strange result often blame the compound when the diluent is the variable. Consistent pH matters as much as sterility, and it is one of the first things cheap manufacture gives up.
Benzyl alcohol content: 0.9% means 0.9%
The preservative load in lab grade product is specified and verified at 0.9%. Import product has been found under-preserved, which shortens effective vial life, or over-preserved, which changes the solution profile.
Either way you are running your protocol on an unverified input. A $2 saving per vial is a poor trade for an uncontrolled variable in every vial that follows.
What this means at the bench
Use lab grade product from a supplier who verifies what they ship. If a result looks off, the diluent should not be on your list of suspects. BuyBac ships lab grade bacteriostatic water in 10mL, 30mL and 5x10mL formats, dispatched from Perth.