I have worked on technology related to the proximity sensors on phones (the thing that’s supposed to detect when your phone is at your ear while on a call) and

I have worked on technology related to the proximity sensors on phones (the thing that’s supposed to detect when your phone is at your ear while on a call) and have known people who have worked on several proximity sensors on several different phones and other devices. These are generally simple sensors but they are sort of hard to quality control in the factory and tuning them generally takes some significant amount of work. The problem for phones without a “notch” like what the iPhone does is that the OEMs tried to put the proximity sensor below the screen. It generally works - but the problem is that the IR pulses emitted by the sensor excite the display and will turn on pixels and create a grey or white spot over the sensor. Product managers later decided that they don’t like this spot, so engineers had to put in all sorts of software mitigation, mostly involving turning off the sensors and making them less sensitive. An expensive phone generally has a larger team of engineers who will tune these sensors, work on the factory quality control problems and generally make things reliable. Apple, with their strong engineering culture has generally refused to deal with the white dot on screen thing entirely by putting the sensor on the notch. Unfortunately with lower end phones, you can’t get the same quality that you will get with a $800 phone. There are people who work really really hard to make things better, but its mostly underfunded engineering teams trying to fix problems in software that honestly should be fixed in the sensor hardware by the vendors.