Re: VR support - they do have an optional proxy driver for OculusVR and SteamVR which attempts to cancel out the effect of motion on the tracked headset position. It doesn't require an additional puck - they know roughly where the platform is at any given point based on the commands they send to it and (if applicable to their system) any feedback position signal coming upstream. Combine this with an estimate of where your head is in the rig relative to the motion axes and pivot points (this is tunable) to get a transform that you can invert and apply to the intercepted tracking data before it reaches the game.
I believe this is the thing you're talking about that uses a tracker to cancel motion:
https://github.com/sharkyh20/OpenVR-InputEmulator
(Though it seems to be getting little support these days)
I've been working on my own VR motion cancellation, similar to what NLR uses (no tracker). It works pretty well. Without it, you end up outside the car on steep banks and hills
Back to the NLR Traction Plus: It's very impressive engineering, and fun to see inside it. I can see the value as part of a package with their seat mover. But, for most DIY rigs, it seems a bit at odds with itself - if you have this kind of money, there's a good chance you have a big heavy rig with heavy corner actuators, and then you're bumping into the weight limit.
To me, it seems over-engineered. Impressive, but too complex for what it does. You can DIY a yaw system for $1k and probably DIY a yaw + sway + surge (which it doesn't do) system for $3k maybe? There's certainly value in having a well-built, turn-key solution... but there's no way I'd feel comfortable putting my rig on top of this. A simpler design likely would cost less and have a higher weight limit.
It's like they over-constrained themselves to designing the perfect yaw + sway platform specifically for their line of cockpits and seat movers, and in the process shut the door on supporting DIY cockpits (but then decided to sell it for DIY rigs anyway).
It's nice to see Barry's comments on the feeling you get from true left/right sway. The GS-5 also tackles this problem, but in a different way. I suspect a sway motion axis would give you a more exciting feeling of weight transfer and change of direction, for example during a turn apex or if a car bumps you (but, you still need the GS-5 for sustained forces). I'm planning to rebuild my yaw platform at some point and have been contemplating whether I should toss in sway and/or surge. If it's anything like the heave motion I get, or snap from a well-implemented yaw system, it could be a lot of fun