[BUG] GAEConfig.average_gae default does not match GAE.__init__

[YeonwooSung]

Describe the bug

GAEConfig.average_gae defaults to True, but GAE.__init__ defaults average_gae to False (class docstring: "Default is False").

GAEConfig documents that every GAE.__init__ kwarg is exposed as a field. Hydra instantiate(GAEConfig) calls _make_gae → GAE.__init__, so leaving the field unset standardizes advantages even though constructing GAE(...) does not.

This is a default-value mismatch on an existing field, not a missing Config field. It is independent of the _CONFIG_PARITY_KNOWN_GAPS tracker in #4228 (GAEConfig is not on that allowlist; default equality is not enforced there).

GAE.for_recurrent defaults average_gae to True on purpose. That constructor is not used by instantiate(GAEConfig) and should stay as-is.

To Reproduce

from hydra.utils import instantiate
from torchrl.objectives.value import GAE
from torchrl.trainers.algorithms.configs.objectives import GAEConfig

assert GAE(gamma=0.99, lmbda=0.95, value_network=None).average_gae is False
cfg = GAEConfig(gamma=0.99, lmbda=0.95)
assert cfg.average_gae is True  # Config default
assert instantiate(cfg).average_gae is True  # Hydra users get GAE(average_gae=True)

Expected behavior

GAEConfig.average_gae should default to False, matching GAE.__init__. instantiate(GAEConfig(gamma=..., lmbda=...)) should produce an estimator with average_gae is False.

Additional context

    average_gae: bool = True

        average_gae: bool = False,

        average_gae (bool): if ``True``, the resulting GAE values will be standardized.
            Default is ``False``.

test_gae_config_instantiates_nested_group_key instantiates GAEConfig but does not assert this default.

Reason and Possible fixes

Set GAEConfig.average_gae = False so it matches GAE.__init__. Keep GAE.for_recurrent(..., average_gae=True).

Checklist

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[YeonwooSung]

/assign