Why are the neurites from hair cells to spiral ganglion cells called axons?
I believe to understand now, thanks to @AliceD's answer to this question:

Why are Merkel cells innervated by an axon, and not a dendrite?



The axon seemingly emanating from the cell (hair or Merkel) is just by coincidence not a physiological part of the cell (hair or Merkel), but its functional axon. The tactile meniscus (in the case of the Merkel cell) plays the role of an "out-sourced" axon hillock of the cell (hair or Merkel) which possesses no axon hillock (and axon) on its own.