No, it’s not. Slow growth leads to a tighter grain, greater density, and reduced moisture content. All of those things make it stronger and more stable. That means less twisting and warping.

Sure, but in practice it's all going onto a pallet and stored in badly humidity and temperature controlled warehouses, where it will dry out, then rehumidify, dry out, rehumidify, and so forth day after day. It doesn't really matter how "good" the wood is, when its storing conditions are shit.

I recently did a renovation on my 1953 bungalow. The Douglas fir studs I removed from a wall are both laser straight and tough as guts. That wood is so hard that you can’t drive a modern nail into it without drilling a pilot hole first.

As a carpenter, I really have to ask you, why would you ever want this though? Sure, you may only need a post every 6 feet, but in reality, nomatter the strength, you're going to frame it to be compatible with with your interior lining. Strength of wood is seriously not needed or wanted today. It just makes the wood expensive, heavy as fuck, and difficult to work with.

And while the wood may very well have been very straight, that's what happens when you nail it into a frame, which will straighten it out, and place it in a controlled environment like inside a wall for 70 years. It's going to conform to that shape. I have seen plenty of dense wood in buildings be crooked as a bow, because it wasn't limited in its movement, or because it wasn't shielded from constant change in the environment.