You may be missing the fact that the 28-75 is an FE lens.
From the article:
At the moment, Sigma offers a 24-70mm F2.8 for $1,299 which you will need to add the MC-11 converter to make it E-mount compatible. It costs an additional $249. The Tamron 28-75mm zoom comes in at $799, or about $800 cheaper.
I like the format of the article but I’m fairly disappointed by the use of a clickbait title.