The tilt lock mechanism is, and was never designed to hold the motor up during trailering. Yamaha even put out a bulletin on this many years ago on some of the PT&T motors being supported solely by the PT ram (not the trim rams), the constant bouncing of trailering the rig takes it's toll on it. Same bulletin referenced the tilt lock pin on the PT&T motors, as well as the manual tilt motors being tilted up while trailering. In a nutshell, trailering with it up is hard on the tilt locks. It is also harder on the transom. I learned this myself. Old boat (9.9 on a Ouachita 1432) I usually towed it with the motor all the way down. There were certain areas that I fished where I had to leave it tilted up down some nasty dirt/gravel roads. Wasn't long and I noticed transom cracks, both at the corner braces and at the center brace. Occasionally the motor would unlock during towing down those roads and would fall down off of the tilt lock, then of course the skeg would dig into the gravel/dirt in a couple areas.
All the way down, depending on your trailer and how the rig is set up, it could dig into the roads like mine did sometimes. Concrete is not very forgiving, neither is asphault.
Transom savers are cheap considering the time/cost of repairing a skeg or transom.