It looks like the "double detonation" phrasing is not from Ars, but from the original research paper (Nature Astronomy).

Given the similarities to both two-stage fusion bombs ( https://en.wikipedia.org/wiki/History_of_the_Teller%E2%80%93... ), and to detonator + main charge conventional explosives, it would seem far more reasonable to reuse existing terminology to describe the hypothesized new triggering mechanism for supernovae.