Technically the term tornado vortex signature only applies to velocity imagery, since it refers explicitly to the couplet. From the AMS glossary a tornado vortex signature is:
(Abbreviated TVS.) The Doppler velocity signature of a tornado or of an incipient tornado-like circulation aloft.
From the AMS glossary again a debris ball (or tornado debris signature; they're the same thing) is defined as:
Often referred to as a TDS. A dual-polarization radar-based feature indicative of nonmeteorological tornadic debris present in the radar sample volume. It is typically associated with a significantly reduced copolar correlation coefficient, a low differential reflectivity, and sometimes an enhanced reflectivity factor, which are centered or nearly centered on a tornadic vortex signature.
So the TL;DR is that if its a velocity image its a Tornado Vortex Signature, if its anything else with an obvious ball in the imagery near where the tornado would be expected to be it's a debris ball or Tornado Debris signature.
However, I will readily concede that this is a distinction that a supervisor less experienced with Meteorology the event and the field of atmospheric science in general may not make very clear all the time. Which is why as a former competitor who discovered through this event that I wanted to do meteorology as a career I'm trying to get back to being more involved with volunteering/Event Supervisoring and why I lurk here.