Each sensor seems to have its own "personality" in terms of accuracy and trustworthiness.
Maybe something to do with manufacturing processes, maybe something to do with it's interaction with the body - is it close to a bunch of capillaries, has it been biofouled and clogged up with glucose eating cells? - dozens of reasons why they can differ.
The trick is to be able to figure out the good ones from the bad ones, and, unfortunately, that's a trick which is only picked up after lengthy use.
I know I keep on mentioning blucon a lot (I'm not on commission, honest!), but I'm just very enthusiastic about it. The ability to calibrate irons out a lot of libre inaccuracies.
Many say that dexcom is more accurate. That's probably because it requires calibration twice a day. Without calibration, I imagine dexcom would be pretty sketchy at times too.
William Lee Dubois wrote Beyond Fingersticks... back in around 2009, which is like pre-history in cgm terms. It's a bit dated now, but a lot of his points still hold true, about what to expect, and just as importantly, what not to expect.
I never regard a reading as "true": it's more of a clue or adminicle of evidence which I'll use alongside other indicators to decide whether, in each instance, I'm ok bolusing with it or need bg test confirmation.