Skeuomorphism is a design where there look of an object used for a function is copied in a tool performing the same function.
Like early electric lights where made to mimic candelabra, lemon juice is put in a container in the shape of a lemon or the ‘call’ button on a smartphone has the icon of an analog phone on it.
In the latter case there’s a word thing going on. With the telephone as with the floppy symbol on the save button, there is a point where more people have never used the depicted object. There is a certain point in time where the symbol is used longer than the actual thing.
If that’s the case, can we still call it skeuomorphic?
The problem is that modern smartphones do so much that phone use is a vanishingly small part of their actual use patterns. So if you want an icon to indicate “make a voice call”, it’s probably more confusing than clear. Whereas an old fashioned phone headset indicates exactly and only that purpose.