It does seem to be one of those properties that, if you didn't set it when you had a chance, you can't really access. But you say this property is on the specific layer? I have only ever seen it on the FeatureServer, not the layers.
I happened to have a throwaway layer that likewise had that property set to false, so I decided to use it for testing.
Initially:
Service Description: hatching test 2
Service ItemId: 0c5c1be4122b42fca2aa8706ecfa4356
Has Versioned Data: false
Max Record Count: 2000
Supported query Formats: JSON
Supports applyEdits with GlobalIds: False
I went into the service's Settings and enabled Sync, as I know this setting can add GlobalID fields if they are not already present.
After:
Service Description: hatching test 2
Service ItemId: 0c5c1be4122b42fca2aa8706ecfa4356
Has Versioned Data: false
Max Record Count: 2000
Supported query Formats: JSON
Supports applyEdits with GlobalIds: True
It worked! Why did it work? ¯\_(ツ)_/¯
Toggling that setting back to off does not change the applyEdits property to False, however. I would suggest toggling that setting off and on and see if it changes for you.
- Josh Carlson
Kendall County GIS