It just depends on where the focus is.
The Tamron can primarily shine with very compact dimensions, even more than with the weight.
It extends from 212.3mm (8.4in) to a maximum of 287.3mm (11.3in), but remains very compact for the focal length range and is therefore much easier to transport.

left: Z 70-200/2.8, middle Tamron 150-500, right Z 180-600
It just depends on the range of use, not everyone wants such a telephoto zoom exclusively for wildlife or BiF.
If I want an inexpensive, universal telephoto zoom solution for landscape and wildlife, which I can also take along on a longer hiking tour, then this is certainly an option that has its advantages.
Depending on the price, this can still be a considerable savings for some users.
The Sony version is priced at $1,199.00, which is $500 less than the Nikon Z 180-600mm.