What's the difference? I'm not sure how this renaming would change my behavior.

The difference is that a bug implies that it is an outside influence, a defect is something that has to do with making the thing in the first place. A bug you can see as happenstance, a defect implies liability. Huge difference.

I guess I've over-corrected in the other direction. All of the "bugs" I've ever dealt with were caused by engineers, so perhaps the original meaning (similar to "glitch"?) was lost on me.

The word comes from an insect that got caught in the wiring of one of the earliest vacuum tube computers. This caused the thing to malfunction and removing the insect became 'debugging'... the rest is history. I think it's a fun term but defect is far better for the man made software issues.

A defective device in my mind would have some obviously fatal flaw - it wouldn't even start up, parts would be broken and dangling off, etc. QC immediately rejects it and it doesn't get incorporated into more complex systems.

A buggy device is much worse for any critical application - it appears to work under inspection, and even limited testing, but 1% of the time it develops some fatal data race condition that causes it to fail erratically and cause havoc, e.g. the Therac-25.

So buggy is a subset of defective but it's even worse?

Defects in, eg, pressure vessels can be hard to spot and then suddenly explode when the product is used — sometimes only after a period of seemingly normal operation.

They’re still defects.