[AZLiberty]

Both Rainsong and Emerald use a truss-rod because "the customer wants/expects one".

If you don't have a truss rod, then you can't adjust the relief. How much relief do you like? Proper action is set by the relief, the nut slots, and the saddle height. (and on a few guitars like Taylors by an easily adjusted neck angle). So, without and adjustable rod, one of those adjustments isn't available.

I have wooden guitars where I adjusted the truss rod sometime in the late 90's and haven't touched them since. But I did adjust them.

My Rainsong WS3000 doesn't have a truss rod, and the relief is considerably larger than I like, so I keep it tuned down to lower the tension and flatten the neck. If it had a truss rod, I'd probably put almost a half turn on it and tune to pitch.