I had to get into this years ago because the rule USED to be 6'8" a long time ago, the 6'7" was a change as the result of a NIOSH study in the mid 1970s showing that to be the maximum reach of a woman that was 5' tall, the low side of average height at that time. In the late 1970s, I worked for US Steel and our Allen Bradley MCCs had been designed in 1971, BEFORE the change, so the center of the top most handle in a Size 1 starter bucket plugged into the top space in a section that had a floor sill installed ended up at 6'7-1/2" above the floor, slightly below the old standard but slightly above the new one. We couldn't change it, so A-B came up with a little clip-on handle extension that dropped down to allow that 5' person to reach it. Total PITA but the rules gods were satisfied.
Back then we used to call Exception 2 the "Trapeze Rule", because it supposedly came about as a result of trapeze mounted transformers in factories with equipment drops that were nowhere near columns so there would be nowhere for the disconnect to be mounted that would be in clear site of the transformer. The argument went that since it was FOR that transformer, you would ALREADY be required to get on a ladder ("portable means") to service the transformer, so there was no need to require that the disconnect be lower. The basic concept was that when the equipment that the disconnect was feeding was higher than the 6'7" rule, it was OK for the disconnect to be adjacent.
One potential argument to explore by the way is to bring up 422.31(B) where it says that the service disconnect means can be the panel branch circuit breaker. If it were a motor, 430.107 allows that only ONE of the disconnect means must be accessible, and I have successfully argued that putting a padlock clip on the panelboard breaker satisfied that, so then the switch on the inaccessible equipment just becomes the local equipment disconnect and is OK even without Exception 2. You would be stretching the 430.107 issue because yours is not a motor, but I would bring it up as an example in defense of the concept. Those little padlock clips are often a cheap solution for stuff like this.