Chip antenna too good to be true?
You literally say &quot;I don't trust the swr I measured to represent my system&quot; (and I agree. The worst possible antenna is a perfectly matched termination resistor. Which has perfect swr. I often wonder why vswr is so commonly oversold as metric, especially within the ham radio scene!).
You have a device that calls itself vna - so do some network analysis with it instead of just measuring reflections!
Use your chip antenna as an antenna: use a known to be OK on at least on band antenna as counterpart.
Test s12 with your chip antenna connected to port 1, and more than 1 wavelength away your known antenna, connected to port 2.
If performance isn't worse outside of the bands your other antenna supports, something is fishy.