Before my Acme EZE-Tow, I used a U-Haul dolly and a borrowed Master-Tow several times and had the same question as described above, with my Ford.
The tie-down straps prevented me from locking the steering due to the angle of the toad's tires needed to lock the steering wheel.
So, I just left the steering in the straight ahead position and it had no problems. The steering never turned (much) because the pivot pan did all the turning. I always checked to see if the steering lock ever engaged, but it did not.
Not a perfect answer, but the issue was never a problem for me.
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV