I don't think you should rely on the GUI existing before SerializeState gets called.
If you need to pull values from the controls, test that the GUI exists and fill some defaults in if not. When you create your presets with MakePresetFromBlob() / MakePresetFromChunk() those presets should contain the serialized data that could come from the controls.
MakeDefaultPreset() previously didn't work at all with chunks (unless you override Un/SerializeParams) which it used to call
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