My understanding is that the offending sulkies are a modified version of the standard approved UFO.
The UFO is approved for use in Australia and NZ but I am unsure whether the modified version has or needs approval.
The sulky at issue is modified to assist with horses who strike the wheels struts when racing.
Some are modified width (offending ) whilst others are modified lengthwise.
There is a baseless suggestion in some of the posts of this thread but IMO there are no integrity concerns in this issue and whether some big races were won fairly using a UFO sulky.
It is a matter of whether the modifications are approved within the licencing and wof testing of the UFO sulky.