Here is why we do not delete the out of stock products from the google merchant center
Generally, we do not delete the out-of-stock products rather push them as regular products to the Google Merchant Center.
We do this on purpose because if we delete the out-of-stock products, those products will be permanently removed, and when you restock, you have to again go through the google approval process, which can be time-consuming.
In this case, whenever you re-stock these products, the status will be changed and updated.