Even if the courts won't uphold the copyright, that doesn't prevent people from claiming your videos and initiating YouTube's copyright process against you. This is a recurring problem for people who upload their own original performances of public-domain compositions, particularly solo piano.

An often repeated talking point that's broadly false without further context. Mechanical output on its own can't be copyrighted, that hasn't changed. However it can be if sufficient (as determined by the courts) human creativity went into causing it to be output.