A reed switch (plus magnet and choice of location) would be an implementation of a 'fixed angle switch' per my comment above.

More likely a hall effect sensor, which is solid state and a lot smaller. And yes, older MacBooks had something like that, as evidenced by the fact you could put them to sleep by holding a magnet in the right place (just to the left of the trackpad IIRC in the models I'm familiar with)

When I ran a MacBook Pro in closed clamshell mode and put another laptop on top of it, it went to sleep. Must be a weight sensor in there as well. (/s)

It's one sensor in both cases, and in the latter case you can do so much more: change the thresholds in an update, detect when the lid is in the process of closing, apply hysteresis (on a simple switch, there's an angle where vibration could cause it to bounce between reading open and closed, but with an angle sensor you can use different thresholds for detecting and open and closing state change).

But most of all...you don't have to commit to a behavior early in the design process by molding the switch in exactly the right spot. If the threshold you initially pick isn't perfect, it's much easier to change a line of code than the tooling at the manufacturing plant.

Why use two sensors when one will do? If you already have an angle sensor, it makes sense to get rid of the reed switch and reduce your production costs.

Yeah, my iPhone 11 Pro came with the ultra-wideband chip in late 2019, and before the AirTags were released in early 2021, I believe the only thing it was used was for ordering AirDrop targets by proximity. It was clearly intended for the AirTags from the beginning, but it took about 1.5 years before it actually mattered.

It seems like it would be much quicker and easier to just have a piece of plastic or something cut at a 76 degree angle that they can place on the laptop and fold the screen up to.

76 degrees is just an aesthetic choice?

Sure, but not more than what you're already spending on transforming the image. And it's not like these devices are exactly lacking in horsepower.

But compute is cheaper for the manufacturer than adding a sensor (parts & labor, and it adds up over millions). Someone must've done the math.

The Macbook tally light isn‘t necessarily wired to the camera. It very well could be independently software controlled. At least it was not too long ago. IIRC there was an article about this, posted here on HN.

Macs used to have (still have?) a feature where you could declare it as lost/stolen and remotely take a photo with the camera. I believe the light didn‘t glow for that.

This was correct a number of years ago. Feels a little strange we can just do an API call for bird recognition now.

The Mac camera light is wired inline so as to make this impossible. The only way for the camera to be on and the light not is if the light itself is broken.