> It's reasonable to guess that these devices were made to only explode after a very unique code is is received, and/or only when traffic came over a radio channel known to be used by Hezbollah.
Why is this a reasonable thing to guess?
You don't need to be confused, you can just talk to the person about something else for a bit to determine they aren't an imbecile, then verify their view is actually incoherent by talking to them about it, then write them off as part of the growing group of people that are choosing a fantasy they want to be true rather than the verifiable actual truth in front of them. it's pretty easy to suss out the situation by determining which of the 3 I's you are experiencing (imbecile, irrational, or I duffed it and had my mind changed by talking to them).
Nobody that goes through all that effort of making secret customized electronics and then sneaking them into usage by your foes wants the plan to be ruined because one went off in an uncontrolled/unexpected way, blatantly alerting all the other targets to toss their pagers into a shallow hole.
Even if the engineering makes it's a choice of "all blow up" or "none blow up", they'll also want to have control when that moment happens to be, either to pre-empt discovery and defusal or to coincide with other events and factors.