Dungeon Fantasy Grappling

[oma]

I was reading about grappling and came across this.

Unarmed Grappling Attack. Roll against DX or a
grappling skill—Judo, Sumo Wrestling, or Wrestling—
to hit and establish or develop a grapple.

If I have no grappling skill and a 13 DX. Would I roll at a DEFAULT of Wrestling -2 or whatever? It seems to say that I choose either a SKILL roll or a DX roll. The skill roll would be the wrestling-2 or whatever the default is.

So how does having no training in wrestling let me wrestle better than someone who has spent 1 point in it for example?

Because if I spend 1 point on Wrestling it would still be lower than my natural DX roll, right? Those kinds of rules never made sense to me. Shouldn't I take the same default penalty to my DX roll that I would take to a skill roll at Default? Why do I get to use base DX??