I have seen a few mentions of this in the forum - looks like some action are being taken:
Source: Mazda Valve Stem Seal Lawsuit Alleges Engines Fail
Mazda valve stem seal problems have caused a class action lawsuit for former and current lessees and owners of 2021 Mazda CX-30, CX-5, CX-9, Mazda3 and Mazda6 vehicles.
The Mazda vehicles are allegedly equipped with defective valve stem seals that allow engine oil to leak into the combustion chambers.
According to the class action lawsuit, Mazda has known about the alleged valve stem seal problems since the vehicles were first sold but has concealed its knowledge to continue selling the vehicles. Additionally, Mazda dealers allegedly have either refused or been unable to repair the vehicles.
Source: Mazda Valve Stem Seal Lawsuit Alleges Engines Fail