Having done a lot of python and JavaScript, all I can say is it does matter. It is an extra redirect as you try to find out what is happening as part of a callback (repeated over and over). It is also additional cognitive load as you now need to mentally parse the function's name (which you don't actually care about) and the function's purpose. Finally, it is more time consuming.
I really like coding in python, but the weak-sauce lambdas are on of my least favorite things about it. I would like tail call optimization, but living without it doesn't bother me on a daily basis. Lame lambdas do bother me on a daily basis.