I think I got it--the isolation is from the VAC and the low voltage DC circuitry, but the AC to AC traces doesn't need as much isolation? I see this on the picture of the relay you showed, it's got plenty of isolation between the AC and DC circuit, but the two AC pin (in and out) are much closer.
This was my main problem, getting 6.4mm between AC & AC traces on the board. So I need 6.4mm between the AC and DC circuitry, how much between the AC legs? Is there a chart for that? Judging by the AC current sensor that had AC-IN and AC-out on the four pins of one side of the SOO8, they only had 1mm. I can get probably 3 without any trouble, but if there was a chart of something, I'd like to see it, to understand more about this...
Sure appreciate the the info on this!