Texas is a non-disclosure state which means no state government office can force anyone to provide them with a property sales price.
So, there is a misconception with some Texas real estates that they are not required to provide sales price to MLS. Reporting of sales price is dictated by members mls rules. Most local mls rules require listed properties which sale that the sales price be reported by the listing agent, if approval is granted by the seller.
There is a paragraph in the listing agreement provided by the Texas Association of REALTORS®, where the seller does grant that permission.