Why are my speakers listed as headphones?

Although my Sony Group Corporation WH-100 XM5s are headphones, my Creative Labs Pte Ltd T60s are not, yet are listed as such by plasmashell and kcm_audio:

kcm_sound plasmashell

Does anyone know what the cause is, or how to ascertain what it is? I ask because I believe that they require quite different audio data to sound correct.