Here's the image from the article (which looks like it came from a CoA presentation).
It confirms that it's using gate 13. I think the confusion is that it says "_near_ gate 11". Not replacing gate 11.
and that's what the text of the article says too
"Gate 13, an existing apron-level gate, will be used for busing operations. This model works well for short-term growth that exceeds an airport's current capabilities to handle more flying. A very infamous bus gate in the US, Washington National's Gate 35X, shut down a few months ago but was used to allow the airport to serve more flights as it planned a new concourse. Gate 13 will service three narrowbody aircraft hardstands.
Those three hardstands are a near-term solution, as Austin looks to add six new hardstand positions with a new busing gates facility near Gate 11. This will help service additional flights during the peak hours when there is not enough gate availability or help support the airport in case of irregular operations."