Yes it is standard practice in the industry.
My TT has a GVW of about 11,500. And 5200# axles.
In did some checking into what the differences were between the different rated axles. In my case, it is the springs that are limited to 5200#. The rest of the axle is a 6000# axle. Bearings, spindles, brakes, tube etc. One extra leaf is the difference.
So I could upgrade easily, and may do it some day. What I like about my situation, is that the important stuff (in my mind) is oversized, and will cover the entire GVW of my TT.
You can do the same thing by visiting the manufacturers website and doing a little sleuthing.
You may or may not like what you find...But the important thing is....You will know. With that knowledge gives you the the choice of whether to do some upgrading or not.