Stelo is basically just a consumer packaged version of the Dexcom G6, and in both cases they warn you to use a finger stick to verify unexpected readings. But finger sticks can be really inaccurate, too. For many diabetics it's not a life-or-death matter (only 1 in 4 type 2 patients end up using insulin), and the important thing is the trend over time.
I've personally found my CGM to be really useful in understanding the effect of diet, sleep, stress, etc. on my blood glucose, like the OP says, but you definitely get some weird readings sometimes. Yesterday a new unit told me that my blood glucose dropped below 70 for 2 hours. It definitely didn't! After a while it got itself straightened out in time to scold me for eating some corn chips.