Rey adopted Skywalker and she was related to Palpatine and she wanted to cut her ties of.lineage from the darkside, what better name could she of adopted if not the Skywalkers, this is not that she is a Skywalker. It is a way to carry on the Skywalkers. It's not like she met mace windu in the timeline and decided on Rey windu, the Skywalkers were the only jedi and good side of the force she knew