It's not the most clear statment in the world.
Basically, it means if you use scale wheels, the guardrail and the frog of AM turnout will have to modified (gap narrowed) so the wheelsets don't drop and derail, particularly on the diverging route.
The AM switches are set up for HiRail/Flyer wheels. Scale wheeled equipment will run fine on AM track as long as their turnouts aren't used.
Rusty