Closed Source

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When you buy a piece of hardware with pre-installed software there is trust involved. The software can be open source or closed source, but there's no qaurantee that the software actually on the device is the compiled open source code. When dealing with hardware that has been explicitly designed to prevent data extraction, open/closed source doesn't matter. It's an illusion of security, there is no way to verify what is actually on the device. That not just Mulroy's device, that's any piece of hardware that the user doesn't have access to the firmware. The manufacturer can say that it does xyz when it actually does xyz and abc.

So I think it's not that bad to have closed source code on a device that explicitly designed for maximum security to prevent tampering or data extraction.

I'm saying that without installing the software yourself or verifying the software on a device, it's the same as closed source cause you don't know.
And asking for open source without a way to verify is an illusion of security. The difference is the hardware. Anybody can verify to code bitcoin compile, it, and use it. Unverifiable or un-useable open source = closed source

The same can't be said about application specific hardware. Specifically the using part of that.