App/DAW nonsense. Stereo recording is not an electronic decision. It is a way to use 2 or more mics to create a model of what you would have heard, with your 2 ears, if you had been there when it was recorded. And- it's just a model. If we do spaced stereo recording, with the mics 10' apart, you are hearing what you would hear if your ears were 10' apart (and you were somehow still alive). Probably the most accurate version is binaural stereo recording, where 2 small diaphragm mics are placed in a model of a human head made of ballistic gel, so it has about the same density and acoustic properties as a human head. Either way, taking a mono recording and splitting it to 2 channels doesn't produce stereo anything. It produces 2 channel mono, and as noted above, it doubles the file size for no good reason. If a source was recorded with one mic, it will always be a mono recording, no matter how you process it.