Hey Raquel
There is one situation in which unison will sound identical to double/detuning, and it’s the one you mentioned: A single oscillator, 2-voice Unison, with no spread.
To deal with this in Syntorial, there aren’t SUPPOSED to be any patches that use Unison that way. So if you hear a detuned sound, and it’s narrow, and it sound like two voices, then it’s doubled and detuning.
Again, there aren’t supposed to be any patches like that. However, if you come across one, please use the Help -> Send Score option so we can check it out.