Tire Installation

[Mac549]

I stopped by my neighborhood Discount Tire this morning to make arrangements to have a new set of Goodyear Endurance tires installed on my 2014 Silverback 31RK. When asked how they would jack up the trailer the guy said they would jack it up either where the springs attached to the axle or the outermost part of the axle. When I questioned him he said that is how they always do it. I was under the impression the trailer should be lifted by placing a jack under the frame. Am I wrong? He appeared offended that I would question their methods.
Thanks in advance for the input.

[SeaDog]

If he is jacking under the spring that should be OK jacking on the axle tube is what you want to avoid.