Property tax – Are the appraisals going up when you try to fight?

Hey guys! New homeowner and trying to fight my tax increase. I originally thought that they couldn't / it was illegal for them to raise your appraisal price higher than their initial assessment. E.g. if they say your home is appraised at 500K and that's what your new taxable appraisal is, they can't increase that during the informal or formal hearing or arbitration. But I'm hearing a lot of people say anecdotally that they are raising the appraisal and people who don't settle are getting a rude surprise.

Has this happened to anyone? Can anyone explain or point to info on the HCAD site? I thought this was illegal / against policy.

Thanks!