On my Scamp I have installed a Flexiride axle and I removed an ALKO.
Both of these axles have thicker wall tubing than the frame.
The old Scamp had 14 gauge steel tubing (0.0782") and the new is 12 gauge (0.1094")
I used 1/8" wall thickness on my front end rebuild (0.125").
The axles I have seen are closer to the 1/8" wall thickness.
The 2500 lb axles are 0.149" and the 3500 lb are 0.187"
The axles are quite a bit stronger than the frames.
One question would be if you were talking abut leaf spring axles where the axle is free to move in relation to the frame and could let things more and slip.
expect the junction of the axle and mounting bracket would be strongest in any case.
The axle is the strongest thing under the trailer as it should be.
For safety if the jack is behind the axle it is less likely to shift than under the axle since it is further behind the center of gravity.
I don't hesitate to jack the axle near the frame, but I make sure the trailer will not tip back.
The weak frame is why the caution to not jack up the trailer from the rear bumper.
Also the shell is mostly supported where the frame passes under the front and rear of the shell in four places.
The fiberglassed floor with no other support add little if any stiffness to the system. No my trailer I have added steel 14 gauge square tubing along the sides and to the frame to support the shell all the way around.
IN this manner the shell and frame both reinforce each other and share the load. Thsiss will add stress to the tongue and is the reason for the 1/8" steel tubing with reinforcing.
As always all advise is worth price charged and standard disclaimers apply.
Any reader should study and and decide for themselves, but following the factory suggestions might always be a good idea. In my case since I have rebuilt most of the trailer and have a different axle I will make up my own mind.