Calling the becomeDirty action no longer seems to set hasDirtyAttributes

I have updated to the latest 3.x version of Ember and have got ember-data version 3.28.7. In older versions of Ember (3.20) calling the becomeDirty action on a model set hasDirtyAttributes to true on that model, but in 3.28.7 of ember-data observers that monitor hasDirtyAttributes on a list of models are triggered, but the actual value of hasDirtyAttributes in the model seems to be false.

Has anyone else seen this? I cannot find any links to people having this same issue?

I should say I am using classic Ember objects: Model.extend({})

I get the following results with the following commands:

model.hasDirtyAttributes // false
model._internalModel.currentState.isDirty // true

Looking in @ember-data, it looks like when getting the @tagged currentState it returns this.___recordState instead of the this._internalModel.currentState because CUSTOM_MODEL_CLASS is defined? (Whatever that means.) Anyway the result of the state object thing seems to be false:

model.___recordState.isDirty // false

Why isn't that set to true? Investigating more...

It looks like a lot of things called canary-features have been enabled. In the old version of @ember-data a configuration file looked like:

export default {
  SAMPLE_FEATURE_FLAG: null,
  RECORD_DATA_ERRORS: null,
  RECORD_DATA_STATE: null,
  IDENTIFIERS: true,
  REQUEST_SERVICE: null,
  CUSTOM_MODEL_CLASS: null,
  FULL_LINKS_ON_RELATIONSHIPS: true,
};

but now it looks like:

export default {
  SAMPLE_FEATURE_FLAG: null,
  RECORD_DATA_ERRORS: true,
  RECORD_DATA_STATE: true,
  IDENTIFIERS: true,
  REQUEST_SERVICE: true,
  CUSTOM_MODEL_CLASS: true,
  FULL_LINKS_ON_RELATIONSHIPS: true,
  RECORD_ARRAY_MANAGER_IDENTIFIERS: true,
  REMOVE_RECORD_ARRAY_MANAGER_LEGACY_COMPAT: true,
};

And if I hardcode CUSTOM_MODEL_CLASS to be false things seem to be working again. So now I need to figure out the best way of turning this stuff off without editing node_modules files.

Anyone know if just setting CUSTOM_MODEL_CLASS to false is OK or should I turn off other things?