I haven't quite dug into the source code to confirm my suspicions, but this file lends credence to the idea that this task facilitates accelerometer-based attitude calculations and not gyroscope-based calculations.
From line 274 to line 280 in the file you link to (tasks.c), the TASK_ATTITUDE
task is said to be enabled if the accelerometer device is enabled (in the Betaflight Configurator):
#if defined(USE_ACC)
if (sensors(SENSOR_ACC) && acc.sampleRateHz) {
setTaskEnabled(TASK_ACCEL, true);
rescheduleTask(TASK_ACCEL, TASK_PERIOD_HZ(acc.sampleRateHz));
setTaskEnabled(TASK_ATTITUDE, true);
}
#endif
Given that these are the only times that the TASK_ATTITUDE
task is mentioned in this file, I doubt that this 100 Hz task is related to gyroscopic sampling.