With the way your Cambrian Ridge textures are, I dont think you will find it possible to make it look 100% clean when viewed very up-close. It gets easier the closer in colour and look 2 of the 3 textures are, like in Ian's example. Then having the main seam blend path mapping run along the most defined border (usually, the whole rough border, with both fairway and fringe inside of the main seamblend circle) - different multi mappings can still be used for one same path mapping. And then having the remaining blend (between fairway and fringe) not be a closed loop. But the ends of that one will still be slightly iffy no matter how you do it, I believe. And then its a matter of fiddling with the ends of that one to make the weird area as inconspicuous as possible, which is a lot easier if those two textures look similar. In your case, you could consider if you're ok with editing the fringe texture to look a little closer to the look of the fairway, then I think you will find it a lot easier. Which alphas one uses can matter as well, some are slightly easier to make things look clean with than others.
That all being said, I dont think players really tend to notice those small spots if they look slightly odd, it is mostly the designer themselves that see it. Either way, it can be a lot of extra work if you want it to be as invisible as possible for the player - at least if you dont want the fringe and fairways to look too similar - and it might not be worth that extra trouble. As you say, wrapping around or dividing fairway and green with rough, or having fairway and fringe look identical visually (you can still have different display names for them), is a LOT easier, and if you say you are fine with the rough divide one, I think that is great and recommend that
If insisting on trying it the hard way, and are ok with sentancing oneself to extra work in order to satisfy one's perfectionism...... one other thing can possibly help minimize how noticeable the odd spot is.
One can leave the secondary seam blend (e.g. fairway to fringe) with a non-seam blended gap at the ends so that it doesnt touch the main seamblend (e.g. rough to fairway/fringe) - though honestly, one can try it with it partly touching too, like in Ian's example - and have that last triangle face be the seamblend texture, but with a custom
planar mapping that one rotates (and possible scales) per each spot to line it up correctly (again - Im not saying it is worth the extra work). I tried this on Nine Bridges, which will be coming out soon, and I think it worked pretty well in some places, still not 100% perfect but I tried it on some spots where all 3 textures were very different in look (such as spots with fairway, rough and bunker sodwalls all meeting in one spot) and still was able to be satisfied with the results at the end. One problem with that method is that seamblend textures with planar mappings apparently use the Display Name and Category (as opposed to Seam Blend Terrain Properties) of the seam blend texture itself, and that whole planar face will play as only one terrain property and lie icon. Not a big deal because you can make the area very thin and small, and I made them display and play as the "best" texture for the player (in my example, fairway), so even if the player ends up in that very exact tiny spot where it looks slightly more rough than fairway, they at least wont be penalized and instead lucky - and as such hopefully happy. Not a problem with fringe/fairway really, since both play the same and tend to look fairly similar.
Yet another idea I've thought of, but havent tried yet, is to simply make a custom texture with the 3 textures blended perfectly on the texture itself, same problem with only one category for the area though, and in this case it will cover a bigger area than in the method above. There also remains the issue that you still need to have at least one seamblend end up against the texture though... but I have an idea on how one might be able to do that too... Not sure if it would actually work, but if it did, it would be the visually cleanest solution.
Sorry for unnecessary rant.
P.S. Those Cambrian ridge bunkers from the earlier posts in this thread (look fine, but) werent the insanely beautiful ones I thought of, yet I feel pretty certain it was you who posted about the 8 direction lip mappings and showed such a beautiful bunker, cant find the post now, might have been on the old forum and/or an older course of yours? I see they look different now though, might have been them, but I wonder where the post Im thinking of was then.