Sounds like pretty much everyone reporting sonic improvements from switching to a dedicated streamer so far had a macbook or macmini before.
Personally I wouldn’t use apple for a door stop, but I’m biased that way :)
In any event, it’s not surprising because no computer puts out great audio in factory configuration, notwithstanding the belief that apple "sounds" better, and apple supposedly uses / used a slightly better audio / DAC chip in at least some of their products. That may help a little if you plug desktop speakers in your macbook, but in a more serious listening configuration the PC’s onboard audio circuitry is bypassed.
A dedicated PC can cost more than some used streamers, but the main point of a PC is its almost limitless configurability, giving users the peace of mind that they will never be locked into inadequate, subpar or obsolete proprietary software.