A little tidbit that I've observed anecdotally is that macOS seems to treat modern SSDs differently than it treated my platter based hard drives in the past. If you're feeling adventurous, try this sometime:
* Take note of how much space is available on your drive,
* Create a particularly large file, such as a disk image,
* Note again the space available, and
* Drop that file in the trash and empty the trash.
* Note one more time the space available.
When I've done similar activities, I've noticed that the available space on my SSD isn't always returned to its previous levels after deleting the large file; in fact, depending upon various factors, it might not change at all after the deletion.
More interestingly, if I subsequently open the BootCamp installer (which probably isn't an option for you on your newer M1 Mac) and start to go through the motions of preparing to install Windows, one of the preparation steps will force a disk cleanup routine to run and I'll abruptly get back the space that had been allocated for the deleted file, and potentially other space as well.
So what can we learn from this peculiar anecdote? Well, one thing we might learn is that not all disk cleanup operations happen immediately, even those associated with file deletions; sometimes, macOS waits until there's an actual reason to perform those cleanup ops. Other times, macOS probably waits until there's clearly no user activity, so as not to eat up processor cycles that the user might prefer to use for something else.
This kind of behavior isn't necessarily intuitive to someone who has already formed the habit of suspiciously eyeing every technical detail of the computer's activities, as most any competent Windows user is likely to do. This highly vigilant monitoring becomes second nature to Windows users... because quite frankly, there are far too many reasons to not trust Windows. You're forced to second guess things all the time, whether through Microsoft showing you a wall of checkboxes which all ask in different ways how much of your freedom and privacy you're willing to give up, or through the actions of third party software, some of which could very well be far more malicious than those checkboxes. But the macOS behavior could be viewed as perfectly reasonable behavior, if you're willing to accept that it is doing these things as part of an attempt to make the user experience better, and thereby start learning to trust your computer, for a change.
I know... it's hard. Personally I use Macs, Windows and even Linux for various tasks in my own home, and those Windows boxes still give me pause now and then -- and of course, that skepticism creeps into my observations of my Macs as well, as a result. (How else would I have noticed my own disk space anecdote, right?) But, IMHO, learning to trust your computer a little bit more is an integral part of the whole Mac experience.
So, to echo one of the sentiments offered by others in this thread: I would recommend that you try to worry a little less, so that you can enjoy your Mac a little more.
(Apologies for the long-winded commentary, but hopefully you got something useful out of it.)