I’ve not had an opportunity to really dig into the new changes in 2.3.0 - Such as the addition of the “Salable Quantity” Column on the Products page (backend). Apparently:
- When an Order is Placed, the Quantity field is reduced to reflect this
- When an Order is Shipped, the new Salable Quantity field is then also reduced
I haven’t put much thought into this new change, but I guess it makes sense… I had a quick look and I don’t see any way to disable this new change, so I guess it’s hard-coded in and we’ll all have to accept the changes.
Anyway, I was unable to reproduce your issue. In my 2.3.2 Sandbox I have everything under Stores > Configuration > Catalog > Inventory set as “Use system value” with the exception of Display Out of Stock Products which is set to “Yes”.
If I were to hazard a guess, I would say that the Data Migration Process that you used probably wasn’t compatible with Magento 2.3.x. Therefore, it Migrated all of the M1 data but didn’t set the Salable Quantity value because that field didn’t exist before.
At this point, I would:
- Check your Data Migration Process to see if there is an up-to-date version that accounts for this
- Reindex your Database (on the off chance there is an indexer that recalculates everything correctly)
Further Reading
- Managing Sources (Official Magento Docs)
- How to reindex Magento 2 manually