Unclear documentation of noise defaults constants

[ZacharyVernec]

Hi,

I want to improve documentation of GenericBackendV2, in particular the noise_info constructor parameter. For this I need to understand where the constants _NOISE_DEFAULTS, _NOISE_DEFAULTS_FALLBACK, and _QUBIT_PROPERTIES come from.
Are these values taken from an average, best case, worst case of IBM processors? Or from a wider range of quantum processors in the field?
I see @ElePT updated these values in PR #11785, is there an intention to update them again in the future?

Thanks.

For reference, the following is the code snippet where these values are defined:

# Noise default values/ranges for duration and error of supported
# instructions. There are two possible formats:
# - (min_duration, max_duration, min_error, max_error),
#   if the defaults are ranges.
# - (duration, error), if the defaults are fixed values.
_NOISE_DEFAULTS = {
    "cx": (7.992e-08, 8.99988e-07, 1e-5, 5e-3),
    "ecr": (7.992e-08, 8.99988e-07, 1e-5, 5e-3),
    "cz": (7.992e-08, 8.99988e-07, 1e-5, 5e-3),
    "id": (2.997e-08, 5.994e-08, 9e-5, 1e-4),
    "rz": (0.0, 0.0),
    "sx": (2.997e-08, 5.994e-08, 9e-5, 1e-4),
    "x": (2.997e-08, 5.994e-08, 9e-5, 1e-4),
    "measure": (6.99966e-07, 1.500054e-06, 1e-5, 5e-3),
    "delay": (None, None),
    "reset": (None, None),
}

# Fallback values for gates with unknown noise default ranges.
_NOISE_DEFAULTS_FALLBACK = {
    "1-q": (2.997e-08, 5.994e-08, 9e-5, 1e-4),
    "multi-q": (7.992e-08, 8.99988e-07, 5e-3),
}

# Ranges to sample qubit properties from.
_QUBIT_PROPERTIES = {
    "dt": 0.222e-9,
    "t1": (100e-6, 200e-6),
    "t2": (100e-6, 200e-6),
    "frequency": (5e9, 5.5e9),
}