Although everything I've read/heard about your Escape indicates that you're probably right about the tow package being mostly external, I think you should ask a Ford dealer directly just to make sure. From what I can make out in specs/other conversations, it looks like extra cooling/torque/rearend enhancements have been made standard in that trim/engine level.
That's assuming we're talking about a NEW Escape.
One thing I'd caution about, though:
Aftermarket hitches often differ substantially from those that come from the factory installed. I don't know about the Escape, but in the case of the Subaru Forester, for example, the factory hitch is an "integrated"-type system that includes more than a dozen mounting points, some of which actually are internal to the vehicle's frame structure. By contrast, a supposed 3500 pound aftermarket hitch for the same vehicle from E-trailer has many fewer mounting points and all of them are external, mostly to sheet metal.
Hitches are not all created equal, and if such differences exist with the OEM Escape hitch they may well account at least in part for the very clear "only with factory tow package" language attached to that 3500 pound max.
I recommend that you clear this point up very carefully with a competent Ford technician before proceeding with your shopping.
" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien