Forward fix for same_shape oblivious guard (#119383)
Fixes internal test
```
buck2 test '@fbcode//mode/opt' fbcode//accelerators/workloads/models/slimdsnn:slimdsnn_test -- --exact 'accelerators/workloads/models/slimdsnn:slimdsnn_test - test_generate (accelerators.workloads.models.slimdsnn.test_slimdsnn.SlimDSNN)'
```
And I added an OSS test that approximates the internal situation.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Differential Revision: [D53544208](https://our.internmc.facebook.com/intern/diff/D53544208)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119383
Approved by: https://github.com/atalman, https://github.com/albanD
