The typical cast bullet diameter for 9X19 is 0.356", which can certainly vary from different sources and batches. Typical jacketed bullet diameter is 0.355". I suppose that some cases will be encountered with slightly thicker case walls, and if combined with the larger cast bullet diameter the result could be a round that exceeds the minimum dimensions, as measured by your gauge (and your gauge was also produced with certain manufacturing tolerances). Doesn't necessarily mean that the round won't feed, chamber, or function properly in your pistol.

If it passes the "plunk test" in your pistol's chamber it should be good to go.

I have loaded 9X19 with cast bullets of 0.357" diameter; they function just fine in my Browning Hi Power but will not function at all in my Smith & Wesson pistols.

Everything involved (case, bullet, pistol, cartridge gauge) was produced to manufacturers' specifications, each of which included some degree of manufacturing tolerances. Certain combinations may display a cumulative effect due to the combined results involved.