Nope. It's been what, only 2 years in to NASCAR actually having EFI engines? Even then, the teams were restricted from being able to use all of the data from the ECU, so everyone had to run at gimped tuning.
V8 Supercars, for example, debuts more tech in one race than NASCAR does in a season. Even WRC Rally cars are questionably more complicated.
Nascar is low-tech in many ways. The car bodies must fit production sedan templates, so the the chassis is welded tubular steel instead of carbon monocoque like on F1 or Indycar. The engines are carbureted instead of fuel injected. There's no turbochargers (although Indy just got those back this year as well). There are strict rules about spoiler size and type.
They do make extensive use of sensors and telemetry, but the cars themselves are pretty retro.
Isn't that a common myth?