When a synchronization begins, by default, all the current status are stored and the status is changed to Processing. This way, the system avoids a new update when an item is changed.
Once the synchronization is over, the process restores the indexers to its status original and begins a full reindexing.
You need to take into account that...
- In case you have an external plugin ( for example, Elasticsearch) controlling Magento indexers
- In case there is any modification through console
...the indexers could be reactivated in the middle of the synchronization, generating incorrect data in the index tables.
If you want to manage the indexers through any of the above channels, the option of ‘managing the indexers’ in Sales Layer plugin should be deactivated.