This other review seem to suggest the same 12, 13 hours.Battery claims are almost never right.
https://www.t3.com/reviews/samsung-galaxy-tab-s4-review
It may not be 16, but it's more than the 10 hours you can get with the iPAD. Something Apple should improve, if possible.
Anyways, it looks like there isn't going to be a 256 GB wifi + LTE version. Only wi-fi. I was only able to find a 64 GB, and apparently it can only work with Verizon. I couldn't buy from the U.S. and bring overseas, to use different SIM cards (4G) from other ISPs.
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And a few more details: