Yes, the various charts and gauges don't really match. In my collection of antique steel knitting needles there are sizes that don't match any needle or wire gauge that I've been able to test. I think that different needle makers used whatever wire they could get. The change in needle sizing in the middle of the 20th century doesn't help; six or eight of the finer sizes were dropped and the others were renamed, so a "size 18" needle from earlier will be different from a "size 18" needle after the change.
And then even the metal gauges wore out over time, so the holes grew larger.
There's just no substitute for checking the gauge with a swatch.
=Tamar