Using dev kits to project what a consumer device is going to be, opens up for potential issues as decent Dev Kits have typically always ran with a few changes in hardware to aid in development. I.E. More Ram or faster CPU/GPU etc' to account for profiling and logging tools overhead.
There was a mix up but there is an OLED screen Switch model.
If anything leaks are more accurate today than in the past, in the past almost nothing leaked about major hardware, these days there is info definitely floating out there before hand on virtually every major hardware release.
NX being a hybrid console with detachable controllers was leaked months before, PS4 Pro and XBox One X were leaked, Switch Lite was leaked (right down to an actual photo of the back plate of the console), Switch OLED was leaked.
Sometimes the info gets a little mixed up, but it doesn't mean rumors are not ever worth listening to, quite often where there is smoke there is definitely fire these days.