Just last night skied mine with both Rotte 3pin with cable and Nato M98. Better kick and glide with 3pin as expected, best support with 3pin +cable.
I got my Guide Expedition BC's on a bargain 2 yers ago. Found them one size too big, but have not sold them due to thinking they make excellent extreme cold boots. Last night was tinkering with the fit, and got it right. Now that they fit me and having tried them with 3pins, I must say that it is a true pity that one cannot rely on them with 3pins. The sole is very flexible, which makes them the best k&g 3pin boot I ever tried with a huge margin (no experience with Alaskas or other true softies), but somehow the package manages to feel supportive with pins only, let alone with cables. Very smooth, very flexible, but firm support.
This far had used them with M98s/Rivas, and they do perfectly ok on flats and downhill, apart from the squeak, for utiltarian use. 3 pin cable just makes them shine as ski boot.
Boot sole structure is something new to me. The sole is very thin for a 75mm boot. It consists of a thin outer sole, and an eva (?) midsole. Eva layer starts roughly 8cm behind the tip of the duckbill, upper part of the duckbill being rubber and glued to the outsole. Is it a common structure? Does not raise confidence on their durability with 3pins. I suppose that it would be much stronger if made out of a solid piece of rubber instead layers with eva. The sole could even be a mm or two thicker, I am sure that it would develop a good flex over time as these are boots to last possibly decades. Of course the eva midsole has a function on thermal insulation too, but I would not see losing that as problem. In fact i added a 6mm hd eva insole inbetween the shell and inner bootie, still plenty of room for the toes.
So, in short. No, I do not think they can take prolonged 3pin action, but I truly hope they could. I have the Xplore version coming in soon, but promise to buy two pairs of 75's if they are made 3pin compatible. They are the kind of boots I want to grow old with