Goodyear Ducaro GA

I bought a tyre depth gauge to play with and I wish I'd bought one years ago, much easier to use than vernier calipers, anyhow my tyres as per the title heading have 6 mm of tread depth remaining, this didn't look good so I measured the unused spare and it has 7 mm of tread, so it appears I've used 1 mm in 1130 km of driving, at that rate when it gets down to my change tyre zone of 3 mm they shall have only done some 5000 km or so, much like a bike tyre.
It all sounds very suss to me, maybe they have a supersoft top layer so all the journalists write impressive articles about grip levels, then have a hard as iron layer further down where no journalist would ever discover, but regardless and despite me having no complaint about how they drive I was never going to buy these as a replacement anyway.
They actually have a UTQG rating of 240, which is very high by Australian standards where traders insist on stocking tyres with extremely grippy soft compounds with great wet weather handling that are well suited to our long straight dry roads, meanwhile the rest of the world have to be satisfied with long lasting UTQGs of over 400 so as to not bother the tyre shops every few months.