It's not wrong, that's actually a procedure recommended by some mfrs. Get the TT slightly nose-down, then drop the rear stabilizers. As you bring up the tongue to level the TT, you're bringing some of the weight off of the suspension, so when you drop the front jacks the trailer is more solid than it otherwise might be.
Obviously you don't want to jack the wheels all the way off the ground, so the TT has to be only slightly nose down when you drop the rear jacks.
Also, most mfrs will say to level the TT before you run the slides out, not before you drop the jacks.