Hello,
Thank you for reaching out to us.
The visibility of your extension has no effect on the review time. Private or public, all updates will be treated the same by the review team.
Please note that both new item submissions as well as updates to existing items (*including unlisted/private) are subject to automated system checks and may be flagged for manual review. For the reason of being flagged to the additional compliance review is not shareable with you due to security purposes. Please also note that you cannot modify/update your item or cancel the review while it is in progress.