it sounds like Britney is nowhere to be found to my ears
even on Scary's stems it doesnt really sound like Britney. im having a hard time believing that Britney actually sang lead vocals on that album either.
we know Circus was supposed to be her true "comeback" album and era, and was supposed to be the end of the C-ship but then the tour concluded and the C-ship was still there. then after that it really could have gone one of three ways - 1. she put her all into FF album hoping that would be enough to get her out of the c-ship, that failed and she half-assed the tour in retaliation, 2. she half assed the FF album knowing that the c-ship will never go away but still wanted to record material for an album because she loves her fans enough to not fully give up on them, 3. fully gives up on everything after the Circus tour and her father has Myah stand in for Britney on future albums.
i think after the backlash from fans over the mess that Britney Jean was, they let britney have more creative freedom over the next album (originally was supposed to be an EP titled Pretty World (with real-life van promo and everything) that had Pretty Girls as the lead single, scrapped it, and then later came up with the single Make Me... and the album Glory).