Reproduction steps:
1. Open the attached project ("case_1229273-PresetPropertyModifications.zip")
2. Open Editor window via "Window -> PropertyModificationsWindow"
3. Drag the 'TransformPreset0' asset from the project window into the object field in PropertyModificationsWindow
4. Observe Preset.PropertyModifications returning an array of 14 elements
5. Exclude all properties for 'TransformPreset0' asset via the inspector context menu (three dots button to the right of asset name in the inspector)
6. Observe all property modifications returned are empty
7. Include all properties one by one via the 'TransformPreset0' in Inspector - Right-click "Position", "Rotation" and "Scale" and click "Include property"
8. Observe Preset.PropertyModifications returning an array of 24 elements
9. Include all properties for 'TransformPreset0' asset via inspector context menu "Include all properties".
10. Observe Preset.PropertyModifications returning an array of 14 elements while asset inspector looks the same

Expected result: Preset modification array length remains the same
Actual result: Manually including all the properties after they were excluded yields a preset with more elements in modification array(in this case 24)

Reproducible with: 2020.1.0b6, 2020.2.0a7
Couldn't test with: 2017.4 (presets not supported), 2018.4, 2019.3 (manual include/exclude of fields is not supported)