You mean false advertising? Because unless is it an actual overpressure system, using compressed and probably stored air, that VX gas is getting in.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7158270/
"In principle, homes could be outfitted with High-Efficiency Particle (HEPA) filters, although this would require substantial modifications to most home heating, ventilation, and air conditioning (HVAC) systems and would require positive overpressure systems to prevent infiltration through cracks. However, hermetically sealed office buildings frequently have HEPA filters and positive overpressure HVAC systems, making it easier to ‘harden’ such buildings if they are likely targets of attack or if they perform critical functions in the midst of an emergency."