Apple may optimize or recompile apps from time to time. It might sound creepy “oh gosh they can redeploy my code without my explicit consent” but in reality it serves everyone better.
The recent Meltdown and Spectre vulnerabilities need to be fixed on several fronts. Recently some patches were made to the LLVM compiler to reduce or eliminate the chance of a Spectre attack: after recompilation the resulting apps are less likely to be the victims of a return-oriented-programming attack (a type of crack) under a speculative execution environment (ie running on a modern high performance processor).
Since not every developer is able to maintain their app (or in the case of Waytools, the publicly published TextBlade app is out of date as compared to the TREGgers version that is under beta testing), Apple probably thought they were doing everyone a favor by recompiling the old app.