Upon closer inspection, this guide rod appears to be a type of "recoil reducing" guide rods like Menck, Harrrts, or Sprinco.
Under normal operation, the hole in the end of the slide glides down the length of the "passive" stock guide rod compressing the recoil spring.
With this "recoil reducing" type, the slide also glides down the rod until it reaches the raised ring near the rear end of the front section of rod.
When it reaches that ring, the front section of rod begins to compress the plunger spring in the rear section, affording an addition amount of spring resistance in the last 1/2" of slide travel.
Somewhat like a "shock buffer" without reducing overall slide travel.
An ingenious bit of gimmickry, although I'm skeptical of its utility.
John