I guess the whole “point” of memory playback is that there is no disk activity during the play. (So starting the play during the disk load basically nixes that “point”..)
Memory Playback should be for eliminating the impact of slow disk/network access interrupting/delaying playback, since that is a real thing which can actually happen.
An ideal memory playback system would be accessing your disk while audio is being played back from memory, to queue up the next track (or buffer multiple tracks) so that playback never happens directly from the disk/network, while keeping memory usage relatively low (<1GB).
Making an exception to start playback faster on the initial track seems acceptable to me.
I think the idea is (was) that in days of yore, the HDD generated power spikes on the mobo that had a negative audible impact on its DAC. Personally using a modern mobo, a modern SSD, and pushing digitally to a remote DAC (rather than doing the DA conversion onboard), I can’t notice any audible differences between in memory and not.
If you are hearing "interference" with disk access, USB devices etc. it is caused by bad/faulty hardware (e.g. the Schiit Modi 2 USB DAC) or setup issues like ground loops, and will produce
obvious issues with playback.
Memory Playback is not a fix for these issues, as there is a never-ending rabbit hole you can go down to try and "silence" a PC's internal components when you are using a bad/faulty DAC or have ground loop issues, instead of fixing the actual problem causing this to be audible in the first place (the device/setup).
I don't have the source to hand, but I seem to recall there being a test of the Schiit Modi 2 DAC - which is known to have a faulty USB implementation that 'picks up' all sorts of interference from the computer - demonstrating how its performance was affected by things like CPU load and other USB devices being used. Memory Playback
may have helped reduce these problems.
Adding an expensive USB isolator completely fixed this issue with the DAC.
But replacing the $100 Schiit DAC and $260 USB isolator with a $60 Behringer audio interface that has a properly designed USB input performed flawlessly on its own, without having to worrying about things like disk access and USB devices.
Memory Playback has a purpose, but it's not related to audio quality.