There are not exceptions. There are three options (since TCJA).

"(so if they paid for items that they didn't receive yet, it would be included in inventory)"

Not for the "deduct it now" option. Here's a snippet from a nice article with a reference table for that "deduct it now" option:

https://www.eidebailly.com/insights/alerts/2022/12/small-taxpayer-inventory-safe-harbor-methods

"Taxpayers must treat inventory consistently in all accounting records. To currently deduct inventory, taxpayers must stop tracking inventory on all accounting records.

For example, a taxpayer wanting to deduct the cost of inventory when purchased would need to stop tracking the inventory on their books and records and could not reflect inventory on their balance sheet, general ledger, trial balance, tax return or other accounting report. They could continue to maintain an inventory system that tracked quantities of items on hand for re-ordering purposes but could not reflect an inventory asset on their financial records for any purpose."