Well, I can see from the responses so far that there is no standard description of a "Pleading the Fifth" hole.
The hole in question is a long par 4 that has no bunkers. The green is large, elevated with a 10 yard deep serious false front with a back right upper plateau and a lower back left plateau. Clearly the green is the focus of the hole.
The architect in question is Steve Smyers.
I've come across a course guide describing each hole and here's what it says about this one:
"
This is one of my favorite holes on the course,” the designer admits. “It’s a long hole that is reminiscent of the fifth hole at Augusta National because of the type of shot it affords the player on their approach to the green.”
Smyers knows all about that particular hole at the Masters venue. As a member of the USGA Executive Committee, he has served as the hole official at No. 5 during the Masters and watched young players, trying to approach the green with high lofted shots, struggle to get close to any pin cut on the upper, back ledge. “Tom Watson came in there – this was just a few years ago – and he hit a bump-and-run shot , landed it well short, rolled right up and he was the closest one to the pin,” Smyers recalls.
With its false front and gentle spine that divides the upper plateau left and right, the 15th at the Eagle Course will accommodate, even encourage, the same type shots. And with no bunkers on the hole, the entire terrain is open to the ground game."
So, maybe the hole name is just a clever riff on the green being a take-off on the fifth green at Augusta. Or, maybe he didn't want to "incriminate" himself for having "borrowed" the green concept from Augusta. Or, ........................