Let me try this part: "and then adjusted to actual at year end via journal entry (debit/credit inventory and debit/credit purchases (or cost of goods sold depending on Chart of Accounts)."

If this file uses "Inventory Items" then every JE made to inventory asset is a mistake. The Item Names manage the values on hand, and a JE bypasses this. You can see in my attachment that By Item value for the As Of Date is an exact match to the Bal Sheet for that same As Of Date. By Item Names is how you manage "Perpetual inventory" in QB, so you never make a JE. A JE does not provide for Item Names. The function, once you take your final physical inventory for the cycle, is Adjust Inventory.

Now, if they are doing Periodic Inventory, sure. You rebalance between COGS and Asset "Periodically."

And the reporting provides what you asked. You run the Balance Sheet Standard for This Fiscal Year and select the comparison of Previous Period, which gives you, for example, Dec 31 2016 and Dec 31, 2017 as columns.

"One CPA firm I worked with used the clients' QuickBooks profit and loss statement and made a manual entry in Other Costs section of Cost of Goods Sold to account for the actual difference in the beginning and ending inventory balance."

Again, that is only used for Periodic Inventory management, in QB.

In a quick turnaround business, all purchases would go to COGS directly. You JE to asset for the final date of the fiscal year for what still is on hand, and reverse it for the first date of the new fiscal year. Example: Bakery.

In a business such as used vehicles, recreation vehicles, and other large ticket purchases that are on hand a while, you post all purchases to Asset first. Then, Periodically and at least for Year End, you reduce what is on hand to COGS, if that is no longer on hand.

Keep in mind that QB Pro/Premier do average costing. QB Online does FIFO. QB Enterprise does Average, or you can enable FIFO.

Hope that helps. Please see my attachment. In a file using perpetual inventory (inventory item Type, Named stock on hand), you should be able to prove that match.