mobilebert fails returns bad results on CoreML

[metascroy]

🐛 Describe the bug

Result is nan on FP16

sh .ci/scripts/test_model.sh mobilebert cmake coreml-pybind-float16

And result has high MSE with eager on FP32:

sh .ci/scripts/test_model.sh mobilebert cmake coreml-pybind-float32

Versions

Collecting environment information...
PyTorch version: 2.9.0.dev20250725
Is debug build: False
CUDA used to build PyTorch: None
ROCM used to build PyTorch: N/A

OS: macOS 15.5 (arm64)
GCC version: Could not collect
Clang version: 17.0.0 (clang-1700.0.13.5)
CMake version: version 3.31.6
Libc version: N/A

Python version: 3.10.18 (main, Jun 5 2025, 08:37:47) [Clang 14.0.6 ] (64-bit runtime)
Python platform: macOS-15.5-arm64-arm-64bit
Is CUDA available: False
CUDA runtime version: No CUDA
CUDA_MODULE_LOADING set to: N/A
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA
Is XPU available: False
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Apple M1 Pro

Versions of relevant libraries:
[pip3] executorch==0.8.0a0+8e6c8ff
[pip3] mypy_extensions==1.1.0
[pip3] numpy==2.2.6
[pip3] optimum-executorch==0.0.0.dev0
[pip3] pytorch_tokenizers==0.1.0
[pip3] torch==2.9.0.dev20250725
[pip3] torchao==0.13.0+git2eb4f9762
[pip3] torchaudio==2.8.0.dev20250725
[pip3] torchdata==0.11.0
[pip3] torchsr==1.0.4
[pip3] torchtune==0.6.1
[pip3] torchvision==0.24.0.dev20250725
[conda] executorch 0.8.0a0+8e6c8ff pypi_0 pypi
[conda] numpy 2.2.6 pypi_0 pypi
[conda] optimum-executorch 0.0.0.dev0 pypi_0 pypi
[conda] pytorch-tokenizers 0.1.0 pypi_0 pypi
[conda] torch 2.9.0.dev20250725 pypi_0 pypi
[conda] torchao 0.13.0+git2eb4f9762 pypi_0 pypi
[conda] torchaudio 2.8.0.dev20250725 pypi_0 pypi
[conda] torchdata 0.11.0 pypi_0 pypi
[conda] torchsr 1.0.4 pypi_0 pypi
[conda] torchtune 0.6.1 pypi_0 pypi
[conda] torchvision 0.24.0.dev20250725 pypi_0 pypi

cc @kimishpatel @YifanShenSZ @cymbalrush