As a former DIY:er and reader of many theories ( including Tooles ) and have tried most of them - I dont see ASR or GR research as the only true sites to learn from .
As Goat76 wrote earlier , testing and only listening to only one speaker in a room doesnt show 100% how two loudspeakers in a room , in stereo will perform.
It might be interesting though, to see the freq. linearity of the speaker and also the distortion measurements .
Tonycollinet wrote ( rightly ) that the stereoimage appear in the brain of the listener, and in two channel listening there are reflections from the walls thats playing a big part on how we experience spatial qualities, the ” illusion” of the recorded event .
It takes a lot of experience to install two loudspeakers correctly in a room, because the stereo system is so flawed, you really need the influence of the reflections from the walls in the room, to have a positive impact on what you hear . This demands knowledge of ” the optimal delay” for such reflexes in 2 channel sound . 20-25 ms delay of the wall reflections can positively contribute to a good spatial experience - ruling out small rooms where this is impossible.
ASR or GR research dont mention this , probably because they have not enough experience , or they just dont care much for installement.
Or maybe they realise that the perfect installed two channel system in a specific room with its psycoacoustic impact, dont obey by any fixed rule , impossible to explain in writing … in the end, you have to trust your ears .