The reason you might see that response, is because some version of this question is posted here on TMC at least 1-2 times a day, every day, and has been for at least the last 3 years I have been here. Doesnt make it "right" but if you realize that members here have seen some version of this exact question maybe 200 or more times, it might explain the reaction.
In the model 3 subforum I moderate, I take all those posts and put them in a single thread, so people can search it for answers (and so that the question doesnt overwhelm the subforum). That thread is here:
I purchased a 2021 M3P in June, and drive a lot for work. I've seen the typical battery degradation described by many on this forum since I've put around 25k miles on it, down about 7% from the original 315 EPA range when I got it. However this morning the range suddenly dropped 30 miles and...
teslamotorsclub.com
its 179 pages (not posts, pages), on some variation of your question.
now, I dont think you should (nor expect you to) read that entire thread. You can search it if you desire, and deep dive into the topic. For a VERY " TL ; DR" (too long, didnt read) version.
The car uses an estimate, its not like gas, and a battery is not quite as simple to measure as a fuel tank
The range is based on EPA estimates, and unless one drives like that (like 42 MPH or something on flat land) should be taken as "best case if I drive 42 MPH).
There is a thread I can dig up on the actual algorithms that people have deduced over time, if that is something you are interested in (the EPA algorithms) but to answer the "unasked" general question that comes up around this post, what you are seeing is perfectly 100% normal.
This thread below is on "charge data" and is a more technical one than the one above so those two should get you started. I know this is the model Y subforum but model 3 and Y have the same battery, so 100% of this is applicable.