Had spread axles on my Heartland North Trail. IMO they were there to reduce the TW. From the factory the TW was under 10%. The axles were also placed toward the center too much. Horrible towing TT. I used an EQ with built in 4pt sway control and had a 950lb TW on a 7200lb TT. The TT constantly wandered. Never got into a sway issue though.
To those that say they don't think the scuff is that bad. Well when I have to back into my driveway I need to backup 90*. I always left tire cuff marks on the pavement when doing so. With my current 5th wheel making the same exact maneuver I leave no marks. 5er has standard spread axles.
If spread axles were so much better then all TT's would have them. They put spread axles on TT's for a reason and those reasons may vary. But a well built, well balanced TT shouldn't need spread axles.