If the information is going to be released in full though, and I'm a murderous executive, then why not kill you immediately?
(1) How do you prove you have a deadman switch? How do you prove it functions correctly?
(2) How do you prove it contains any more material then you've already shown you have?
(3) Since you're going to testify anyway, what's the benefit in leaving you alive when your story can discredited after the fact, and apparently it is trivially easy to get away with an untraceable murder?
which leads to (4): if the point is to "send a message" then killing you later is kind of pointless. Let the deadman switch trigger and send a message to everyone else - it won't save you.
People concoct scenarios where they're like "oh but I'll record a tape saying 'I didn't kill myself'" as though thats a unique thing and not something every deranged person does anyway, including Australia's racist politician (who's very much still alive, being awful).
The world doesn't work like a TV storyline, but good news for you the only reason everyone's like "are they killing whistleblowers?" is because you're all bored and want to feel clever on the internet (while handily pushing the much more useful narrative: through no specific actions, don't become a whistleblower because there's an untraceable, unprovable service which has definitely killed every dead whistleblower you heard of. Please ignore all the alive ones who kind of had their lives ruined by the process but didn't die and are thus boring to talk about).