The released version of this lens is without stabilization, then it mainly addresses owners of Olympus or GX7 bodies ... I suppose Tamron made this choice because of price, size and weight and it makes sense (according to me as an owner of two Olympus bodies !
Ratio size / weight / price ; Goog IQ given the range and price
Needs in-body stabilization ; IQ doesn't match HQ zooms or primes