"just wondering about the meter and wondering why this info is so hard to find."
That's probably because for most dancers the idea of meter is just an extra layer of complication that can lead to confusion. Dancers use their rhythm patterns and the musicians use theirs, and if we are lucky we can make them fit together.
"Does Guy Howard mention this 3 beat pattern and dancing to a 4 beat song?"
That's an example of confusion setting in. It is not a 3 beat pattern but a 3 step pattern which uses 6 beats. The Slows use 2 beats each and the Quicks use 1 beat, so the SSQQ pattern uses 2,2,1,1 beats. We dance this pattern to 4/4 music and as you have observed we dance the pattern twice over 3 measures of music. The 2 step and the social rhythm foxtrot mentioned above are slightly unusual in using a 6 beat meter but I would not describe them as non-metered. When you learn more dances and rhythms you will find the dance and music meters match more closely and you will probably feel more comfortable, although there will be some figures that do not fit within a complete number of measures. Try not to worry about it - it's an engineer thing - most people do not notice.
To answer an obvious question: Why don't we dance a 6 beat 2step meter to 6/8 music?
We need to split the 6 beats into 3 groups of 2 for our 2,2,(1,1) but a 6/8 measure of music splits into 2 groups of 3 beats.