Wouldn't it be hard to tell if it's actually working just via the description in the PipBoy, tho? I mean, it'd have to change with every hit an enemy puts on you, or give a large list of all possible weapons affected etc., if that makes sense.
If it worked as intended, I wouldn't be expecting to see the DT changes in my PipBoy display, because as you've said, it could be flickering constantly depending on what's hitting you (especially when you add Hit the Deck into the mix and you go up against enemies with guns, melee weapons, and grenade rifles all at once).
I was actually expecting the PipBoy's reading of my DT to remain unchanged upon acquiring Stonewall. I figured the +5 versus melee/unarmed would be a hidden value which would be in effect against such weapons but not visible in the PipBoy.
It's possible it's fixed, but the description doesn't reflect it.
Assuming it's been fixed, then the PipBoy is reading wrong. It shouldn't display my DT as being +5 higher than it actually is at all times, irrespective of what I happen to be doing. Nor should it reduce to normal once I equip a pistol.
So, either it's working just fine and the PipBoy is giving bugged readings, or the PipBoy is correct and the perk remains bugged. If the PipBoy is correct, then Stonewall isn't really Stonewall. What it really is, is some kind of anti-NRA perk, geared to weaning the player off of guns. "Here, take this perk. It gives you +5 DT against anything! How does that sound? Oh, but it won't work if you equip a gun, by the way. The moment you put a gun in your hands, the +5 bonus goes away. Sorry, but you really shouldn't be carrying guns. They're bad."
A better test method would be to use the console debug text (and have it set to write the info to a text file since it scrolls too fast to read) and check the damage numbers from individual enemies during actual combat & hits.
Perhaps someone would be kind enough to do this? I would, but I don't have the PC version.