Being on but jammed look the same from the perspective of the one shooting them down.
Also, I wonder how resilient it is to the gps spoofing that been going on. If they managed to trick it into identifying itself as a few hundred miles from where it actually was, then very hard to know where it actually is.
All of which is well within Irans technical capabilities.
It is subtantially more likely that this individual plane was tampered with or maintained incorrectly than these signals were anywhere close to being effectively jammed (but still less likely than them not having it on in the first place).
The power levels they are operating at are well into "do NOT stand in front of this" territory
Why? Specs for link16 jamming have been circulating since before the invasion of ukraine, there is a whole DoD technical report dedicated to trying to update it knocking around somewhere.
Iran claim to have used it to bring down US drones in the past.(1)
They jammed the control link so the operators couldnt control it, then used gps spoofing to make its "lost communication fly home" protocol land itself in hostile territory.