The study had people wear electrodes to determine/drive the noise oscillation frequency. The noise oscillator was being controlled by the sleeping human (they used a PLL, which to me implies a bit of "catching up" lag if the human changed frequencies).
However, who's to say that the human has to be in control? You could replicate the study, but have the computer determine the oscillation frequency (or maybe just keep it fixed) and maybe find similar results.
The biggest technical challenge for a DIYer would be "comfortable enough to sleep in" electrodes.
I don't know what he meant by legit, but some white noise videos on youtube feature jumpscares after a while. These are specially bad on people with cardiovascular issues and/or elderly. Always be careful before any kind of meditation-like video.
By legit I mean that they don't pass off white noise or some other noise as pink noise. Try and see what works for you. There is also the YouTube Music app you probably know of that you can use to play something overnight.
