It plays fine for me too but the memory doesn’t represent the size of the file being played. Can you check that?
Indeed, in all my testing I had Raspbian's Task Manager app open and I was watching memory usage in real time... and it loaded the music into memory. I select a song and I notice the memory usage immediately jump up. Even 24-bit/192kHz songs cause the memory to jump (in some cases, by several hundred megabytes within a second or two). And of course, if I stop playback memory usage drops back down to normal.
So it appears memory playback is working fine here. My guess something in your setup causes it to fail for whatever reason, but honestly I can't think of a reason why especially since MC23 appears to be working for you. Keep in mind that in my case I just have my NAS directly mounted on my Raspberry Pi and the library on the NAS has been imported into the Pi's MC that way so I'm not streaming to the Pi.
For a test, you might try taking some local files and putting them on the Pi and importing them in MC (in a test library kind of deal) and see if memory playback works then.