In my mind, abstraction is finding a single representation for various things that share traits. If those things happen to be chunks of code all performing the same task in the same way, then factoring the code into a method would be an example of abstraction. I'm not sure that this definition conflicts with the idea of abstraction being about higher-orderness as another commenter suggests, but I don't think it does.

I disagree with your claim that the 'bad' `average` method is an example of indirection rather than abstraction. Indirection, afaik, is about decoupling two things via an interface so that one isn't directly dependent on the implementation of the other. In this case you are still directly calling the method which will directly execute the code. Maybe the dispute here is around whether we should call these things 'the wrong abstraction' or 'a failed attempt at abstraction' but I think it's a spectrum where you can have a good abstraction but with some parts that don't really belong, and in that case it's still an abstraction.