And you will not see that hold indicator on IC if you do not let the brake pedal free. That hold is always used on parking brake so it’s there even if you come to a stop on any traffic light. That permanent magnet motor function is only available for FSD and is fully electric, meaning the standstill is performed by motors, not by the brakes.
This is quite incorrect.
The parking brake is only used for the park "gear". In cars up to about 2018, this was a separate caliper with an electric gear to engage and disengage a separate set of brake pads on the rear wheels to use as a parking brake. Later, this was integrated into the rear hydraulic brake calipers which have an electric system for actuating the rear hydraulic calipers to double them as a parking brake. Regardless of model/type, the parking brake system has
never been used for any other purpose other than when the car is put into park.
The hold/standstill function, on AP1 and newer vehicle (Q4'14+), is done using the iBooster electromechanical braking system that controls the hydraulic brakes of the entire car. This is how autopilot/FSD is able to control braking at all in the first place. The hill hold system just commands the iBooster to maintain hydraulic brake pressure to keep all of the brakes at whatever pressure was originally commanded.
Never vehicles have an updated version of the iBooster/ABS system that gives finer control (about 2018+), which is how they're able to do the newer regen/brake blending thing, as well as the driving mode that allows completely one-pedal driving. This is all done with the hydraulic braking system via the iBooster. The parking brake is never used for these functions.
This is quite obvious when using any of these car-controlled-braking setups, because the physical brake pedal actual moves as the iBooster is commanded to different levels of braking. Tesla even includes a warning with the new regen/brake blending that the brake pedal will feel different when using it, since it will be already partly engaged during this faux regen deceleration.
The traction motors are
never used to hold the vehicle at a stop, in any variant. This would not only be bad for the motor and power electronics, it would be ridiculously wasteful on the energy front. Holding the car in place on a hill using the powertrain requires generating sufficient energy continuously at the wheels to basically counter gravity's effect of trying to move the car down the hill. The car would have to put in at least that much energy to hold the car still, and this would all just be lost as heat in the powertrain as it strains the motors to perform this task. Instead, more sanely, the car just uses the hydraulic brakes to lock the wheels in place and tells gravity, "Look, you're fight is with friction now. I'm out."
On pre-AP1 vehicles, there is still a hill hold function that activates upon a full brake pedal press when on an incline above a threshold. Since pre-AP1 cars don't have an electronic braking system and instead use a classic vacuum assisted braking setup, this hill hold function is handled by actuating the ABS system's hydraulic pump and valves in a clever way that delays the release of hydraulic pressure from the brakes for about a full second. This pretty much just gives you sufficient time to move your foot from the brake to the accelerator without risking rolling backwards.
I'm not sure where people get the misinformation, like quoted above, but hopefully this clears up how these things work.
