Assange has relied on many people in the past, so there is not much evidence for your claim other than personal sentiment.

What seems more credible is that only he has the keys to some data kept by other persons and he could release these keys via others like e.g. his lawyers. Arresting others who might help him with releasing the data once they have the key makes "sense" from that perspective, although it could be illegal (but IANAL in Ecuador).

A panic button is pretty much the opposite of a dead mans switch.

Which could explain why they waited just over one year after cutting his internet access to arrest him: if after one year still nothing happened, it's pretty much safe assuming he doesn't have a working dead mans switch (anymore).

If true, this could also mean they were in agreements with the Ecuador govt. to arrest him a long time ago.

A dead man's switch is not necessarily based on a timeout when your internet connection is not guaranteed.

If the leak is nuclear level - e.g irrefutable proof that the ruling class ARE reptilians - you want to keep that unreleased for as long as you can.

I can imagine a bot somewhere scanning top 10 international newspapers daily and looking for the words 'Assange' and 'dead' before the countdown begins.