Yeah it is crazy to think that they would use roster space on both Stott and Torreyes. But you also really shouldn't need to. if Didi gets hurt Stott plays SS and Camargo plays third. And then you call up Bohm.
The issue is Didi, and playing time. If Stott and Bohm are your 3B platoon Bohm doesn't get enough of ABs, and Stott misses out on some as well (unless you play him at SS against LHP because he can't be any worse than Didi). And the same is still true if you make Didi 3B.
Camargo is also looking a lot more like a signing that made sense in December but less so now. He can't play SS (really) and his bat is strongest from the same side as Bohm and and Segura (and Castellanos for that matter, who's may yet show up at 3B, though not often I'm sure). His existence does free them up to just stash one of these guys in AAA in the name of playing time though. It's just looking like it will be Bohm.
Actions speak louder than words, and the Phillies' actions are saying they're not at all sure Stott's future is at SS, nor are they sure what Bohm's future is. If they really believe Stott is going to be the SS next year and for years to come (he could just as easily wind up at 2B rather than 3B) they should not be catering to Didi.
But leaving Didi at SS could also be with trade value in mind. Also not to hard to imagine Didi, more than Stott, struggling with position/role change. And then you've got an unhappy negative-WAR player with no position gumming up your roster.
We'll see. Maybe by the time camp breaks they'll do the right thing though if they're not even going to give Didi spring training reps at 3B the decision's kind of already made.