There is no legal requirement that reapportionment be done only every ten years, and district bounderies have often been tweeked between major revisions. I don’t recall hearing of a wholesale reapportionment being done between the decenial reapportionments, but there is nothing in the law to prevent it from taking place.
The nominal justification for the Texas action is that the plan which had been put into place two years ago was imposed by the courts (because the Legislature could not reach agreement), and that it preserved the Democratic gerrymander from ten years before.
Of course, the REAL justification is that the Texas Republicans managed to get together enough votes to be able to push through their own gerrymander, but with stunts like all the Democrats leaving the state to deny a quorum it is hard to muster much sympathy for either side.
The courts have historically been reluctant to strike down reapportionment plans for partisan gerrymandering (as opposed to gerrymandering for racial purposes). Of course, no one can tell what a particular court will do in a particular case, but I wouldn’t get my hopes up…