Yes, the nlbb training concept has been scientifically tested and validated.
The effectiveness of the training was validated in a randomized-controlled study conducted together with the Health Psychology Department of the Free University of Berlin and 232 participants.
Just three weeks use with nlbb significantly reduces problematic smartphone use by 42% and increases well-being by 8%. In addition, impulsive use is reduced by 40%. And the effects have been proven to remain afterwards.
The study can be read here.