Hi, mono noise is great tool for listening your system! When two sound sources output same sound, and you are equidistant to both, both toed-in similarly and so on that sound from source to your ear(s) from both sources is as alike as possible, then you have the pin point phantom center. There are many things that break it, or prevent one hearing it in the first place. For example, if you move sideways not being equidistant anymore it gets loose immediately, good directivity and toe-in can help with this though ( time intensity trading ). Response of the speakers could be different (to any angle) due to manufacturing tolerances, not having DSP to equalize them as close as possible, for example. In addition, edge diffraction makes response vary to any angle. Speaker operation changes with excursion, so on some systems low frequency sound on either side could break phantom center just because the speaker now modulates so much the correlation between L/R is broken. In addition, early reflections from room boundaries and objects could be quite loud, further affecting things even if the speakers were fine. In reality, many people don't pay attention on any of this, and they never have the pin point imaging and it's fine to most.
The important thing is to realize, the pinpoint imaging of phantom center is formed into your reality, into your perception, by your own auditory system! I use this effect to be aware of my auditory system, which then allows to utilize logic on sound I perceive in order to adjust my speakers. the speakers are built by me and it is very important to be able to somehow reason with what I hear in order to try and improve on things with the system, in my room, with my own preference and liking. Believe or not I use the pin point imaging to utilize my own auditory system to be able to reason about the playback system. If you are interested, look for David Griesinger studies about proximity and localization, basically most of his studies seem to touch the subject although mostly in concert hall and live music context, but it's the perception he studies, which we all carry with us no matter if it's concert hall or livingroom.
In short, I've found out that all the rooms I took my speakers into there is some particular size of stereo triangle beyond which this pin point phantom center doesn't happen anymore. But, I've always found it just by moving forward closer to speakers, effectively increasing direct/reflected sound ratio, until at some point the pin point imaging happens quite suddenly. I think this is quite easy to perceive and I think is what Griesinger writes about, it's the auditory system switching state basically. Griesinger calls this distance, where the transition happens, as Limit of Localization Distance. Nice thing with this is, there is no uncertainty with it, it's either or basically and always present in all environments and sound sources as it's your auditory system that is responsible for it, so a lot of logic can be drawn from it.
For example, no matter how small your listening distance, and still not hearing it, then the loudspeakers aren't that great and something with them prevents it. Or, no matter how great your loudspeakers, but if you listen too far too loud room sound (early reflections) would prevent it happening. And so on. I think being able to hear it, finding the transition by ear, takes your listening skill to another level altogether, enables use of logic, confusion gone. You'd learn about yourself (perception), your recordings, your playback system and so on. In general, you can now utilize your own auditory system to your best. For example, some recordings sound weird with the pin point imaging, which to me indicates the engineer didn't have it while making the recording otherwise he would have vomitted doing that all day long. On the other hand, some recordings sound just phenomenal, either side of the transition, with or without pin point imaging. Nevertheless, you'd be always able to listen on either side, at will, just by moving yourself a little further or closer to speakers, utilize switch in your own auditory system. End of circle of confusion.