I noticed for some event properties, the event.isDefault is recorded as False for both preference change values.
According to the current [[ https://meta.wikimedia.org/wiki/Schema:PrefUpdate | schema documentation ]], when a preference is reverted to the system default (and record removed from the user_properties tables), the isDefault should be set to true.
See two cases below I've identified so far but this may extend to other properties as well.
VectorSkinVersion property
| value | isDefault | n_opt |
|-------|-----------|-------|
| "1" | false | 11,271 |
| "2" | false | 741 |
| true | false | 5 |
In addition to all preference values being set to `isDefault = False` in the above data, there seems to be an error in the `event.values`.
The opt in number (`event.value = "2"`) looks correct but the opt out numbers look like they are being recorded incorrectly - it's not clear what the difference between `event.value = "1" `and `event.value = true` (or why `event.value = true` exists)
Data via:
```lang=sql
SELECT
event.value,
event.isDefault,
Count(*) as n_opt
FROM event.prefupdate
WHERE
event.property = 'VectorSkinVersion' AND
year = 2020 and month > 06
GROUP BY event.value, event.isDefault
```
Discussiontools-betaenable property
| value | isDefault | n_opt |
|-------|-----------|-------|
| "1" | false | 1,019 |
| "0" | false | 1,754 |
```lang=sql
SELECT
event.value,
event.isDefault,
Count(*) as n_opt
FROM event.prefupdate
WHERE
event.property = 'discussiontools-betaenable' AND
year = 2020 and month > 06
GROUP BY event.value, event.isDefault
```