Does “strong” mean something specific in regards to alcoholic drinks?

I just bought some drinks from a brand called “Strong D9” which is a 9.9% drink. I was googling the brand and came across a Suntory drink called “Strong Zero” which is 9%.

Obviously when someone says “this is a strong drink”, they either mean strong flavour or high alcohol content, but is there a particular reason brands put it in the label? Like does it actually mean specifically over 9% or something? Or is it just a coincidence?