The only possibility that occurs to me is that the publisher might have claimed infringement of the copyright in its publication, although I imagine that to be unlikely;
I think most infringement claims, at least with Google search results, I'm not sure about YT videos, are done by bots that look for certain things, decide that it's reasonably likely that the content is infringing, and report it. Unfortunately, this is complete bullshit, because they need not have any evidence for their claim in order to get it taken down, but you need to spend considerable effort to get it put back up. Google, YouTube, and other websites will cater to these demands because the alternative (ie requiring the company's claim to be backed up with proof that the content is infringing) would result either in a ridiculous amount of work for the host of the "infringing" content, or the accusing company simply suing the host.
However, even if Ravel's works were still in public domain, I'm not entirely sure it's infringing copyright to post yourself playing them, especially if you're not making any money. You could possibly argue that your playing constitutes a separate work from the original, since, after all, the original is just a bunch of notes on a piece of paper, whereas yours is a series of sounds--hardly comparable
In one of Enzo's videos they insisted that it was Horowitz playing.... 
.... so be it .... we were absolutely flattered.
Were they not curious how your son was able to sync his fingers perfectly with Horowitz's recording? Quite the compliment regardless!
Topic: WHAT THE FREAKING HECK?!????!!????