Raise the suspension? Absolutely.
Stiffen the suspension significantly? Not on a Mopar. I'm not familiar enough with the geometry of the VW's to really say, but I kinda doubt it.
Torsion bars are linear. So not only can you not change the spring rate you don't get any kind of progressive change either. So like I said above, unless you've somehow induced more load on the bars than the weight of the car (and therefore locked one of the control arms permanently onto a bump stop and eliminated any suspension travel), you still only have the the load of the car on the bars, and the spring rate of the bar is the same.
There is a minor effect on the wheel rate from substantial raising or lowering. Basically because the angle of the lower control arm changes its effective length changes, and because the effective length of the lower control arm is a component on calculating the wheel rate from the torsion bars spring rate you can get minor changes in wheel rate. The effective length of the control arm is just with respect to the ground, so that distance changes if you put an extreme angle on the control arm. But it doesn't change very much. I calculated the total swing in wheel rate from the bottom of the suspension travel to the top of the suspension travel at one point and as I recall it was under 10 lb/in and that was on a 300 lb/in bar, not a 90 lb/in slant-6 bar. And the thing is, that effective wheel rate is always changing, any time the suspension moves up and down the effective wheel rate changes slightly because the angle of the lower control arm changes. All you're doing by changing the ride height is changing the effective wheel rate at the static height, with the same suspension travel range you will get the same variation in wheel rate.
And I've done this, I mis-clocked the torsion bars on my Challenger when I first installed my tubular LCA's and 1.12" torsion bars. It was my first Mopar and of course I changed a bunch of stuff. So when I followed the manual, and advice from everyone online, and installed the LCA with it "hanging all the way down" I unintentionally was a hex flat off. With a stock LCA, when it's "hanging all the way down" it hits the K frame before it hangs perpendicular to the ground. With a tubular LCA, well, the narrow width means it will literally hang so it's pointed straight down. The result was that the ride height was obscenely high and couldn't be lowered further with the adjusters. But even with 270 lb/in torsion bars it didn't lock out the suspension. But like I said, that was with tubular LCA's and 1.12" torsion bars which are clocked differently than stock.
With stock LCA's and factory torsion bars you don't really have a hex flat available in the direction that the "kid on the internet" is talking about. You'd have to force the LCA past the K frame somehow so it would hang straight down. But even then, with a hex flat off on a slant 6 bar, all you'd probably accomplish is offsetting the sag in the bar from being 50 years old. It wouldn't change anything else, the spring rate of the bar is the same, the wheel rate of the car would remain within it's usual range, possibly at a slightly different rate than it was at a lower height but the change would only be a few lbs/in, and it would still be an effective rate the car would have when the suspension traveled through that height.
This is literally determined by physics and the geometry of the suspension and it can all be calculated pretty easily. The "kid" hasn't accomplished anything special, and he certainly hasn't significantly improved the wheel rate. Although he may have sacrificed the best geometry if he's raised the car.