Let's rejoin this thread and clarify.
The tag axle has the ability to overextend itself and damage things given the right conditions.
This is why they say to lift it when lifting the bus.
If a shop uses the portable lifts that go under just the drive and steer axle and the suspension is at ride height as the bus clears the ground the drive axle height decreases and the ride height valve calls for air. With the tag unsupported it takes on full air pressure with no resistance and things begin to bend and brake I've seen this type damage on more tag axles than I can remember.
Same with ramps. Unless ramps include both rear axles and u pull up with just the drives same thing will happen the tag will overextended potentially damaging things unless u lift it first.
On a side note when the bus is at ride height there should be slack in the lift chains.