I first noticed this with Michelin crossclimates and queried with Michelin. They confirmed that tread depth new could be as little as 6.5mm iirc, depending on manufacturing tolerances and 7mm was normal.
Ive since noticed a lot of the new tyres Ive bought recently are 7mm including some Conti Premium contact tyres which in the past definitely measured at 8mm.
I still see stated specs eg at Camskill, of 8mm, so it seems to me that some tyre makers are simply reducing the new depth to increase turnover. Continental are vigorously lobbying governments to increase legal minimum treads depths to 3mm as well, so their aim is to reduce tyre life by over 40% and increase sales.
Michelin has stated that there is no need to increase the minimum legal limits based on their testing and real world data from accident statistics.
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