Is tonearm bias a compromise, maybe a myth?

All skin and bones and no meat, which is pretty much what you get when the antiskate is out. I use female opera singers for checking anti skate, I have a couple of records that wont track if its out.

And from the female opera singers Callas is the best also for the antiskate adj. Even those who hate female opera singers need to endure only about 4 cm of the inside groove.

Like Groucho said about Doris Day, "I knew her before she was a virgin."

I was really surprised at how much more depth there was to the soundstage and greater subtle details. I was then gobsmacked by the discovery that I had forgotten to re-attach the bias weight thread! Applying Lateral Bias seems to compromise performance elsewhere, true?

Very true, as Harry at VPI has always maintained and as I and others have described here many times. Pre-loading the cantilever by pressuring it against the elastic suspension reduces its freedom to respond to groove transients. Result? Reduced dynamics and smothering of lower level details... just as you described.

Congratulations on making the discovery for yourself... a perfect example of what I and many others have always maintained: fine tune your setup with the instrument that really matters, your ears!

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AS is a compromise because the amount of skating force your stylus sees at any given moment is constantly changing. There can be no "perfect" setting and chasing after one, by whatever method, is a quest without a destination.

For example, setting AS with a test track optimizes the rig for playing that test track. That's ideal, if that's all you play. As soon as you play music the conditions the stylus sees are different, the amount of skating force it sees is different and that "tested perfect" AS setting just became irrelevant.

The best record for adjusting AS is the one you're listening to. With some carts when listening critically I've adjusted AS from one LP to the next. Fortunately, my present carts sound best with no AS at all, so that's how I play. But YMMV applies here more than almost anywhere in audio.

Keep playin'! Keep learnin'!

Dear Lew, this has nothing to do with 'skating' but probable well with 'bias'. Groucho invented the 'principle of the variable principles' which become the principle of the American foreign policy. Groucho:" if you don't like my principles I have other ''...