I guess it didn't seem to me that the Phillies were lying, they made it pretty clear that they wanted Strahm to pick up some of Ranger's innings, they were just hoping Ranger might be able to give them 2 or 3 as he continued ramping up.
Philosophically it's not that different than what they often did last year - prefer a bullpen game, or include the spot starter in what was still de facto a bullpen game, over a traditional start. If Ranger actually goes on the IL Plassmyer could still make the 26-man, but that could also be an extra reliever (plus Vasquez).
Was Nelson banged up as well? I know Sanchez was. Add in Painter and that's three of your four arms who were supposed to fill the 5th-8th spots (or rather, two of them, but Nelson has started too). But having signed Kimbrel and acquired Soto since they signed Strahm, this gives him a more useful role than he might have otherwise had, especially if he can stretch out enough to get 9-15 outs instead of six.