Lesnars was different as Lesnar walked out on his contract.
WWE does let people out of their non-competes. Chelsea Green was let out of it to go to TNA after her release (it was a couple weeks early). She just called and they're like yeah sure that's fine.
But the 90 days are 100% still enforceable. All the 90 days are is WWE saying "we will release you in 90 days," which is 100% legal. They are still under contract for those 90 days and unable to work on TV elsewhere. Remember when Heath Slater was released and then a month or so later he came out on Raw for a 1-off? He was still under his original contract.