You are correct. You can use any computer as a streamer. I have used, many PCs and MacBooks. I have used different software, tuned the PC to be quiet, and run MacBooks on batteries...also iPads, iPhones etc. However, none of these generally even compare to the cheapest purpose built streamer... like a Bluesound Node (I have one) or WiiM. The PC or MACs are noise generation machines not built to protect the sound quality.
So, while they work... and will sound good at the most elementary level, if you are going for a good sounding audio system you want to get a purpose built streamer... even if it is only an budget Blue sound.
I have used streamers from $350, $3K, $5K, $10K, $13K, $15K and in my main system now I have an Aurrender W20SE ($22K) and each has sound quality better than the tier below. My current one equals my outstanding vinyl rig.
So, yes, you can do it... but if you are interested in sound quality, you should get a dedicated streamer.

