Here's what I have on this, Deb. These are the new PIT tables in V12. 

PIT(Print in time) Tables - Stock valuation summary and detail reports

New stock valuation reports (STOCK12PG and STOCK12PD) are available.  The new reports are available when customer uses the detailed stock accounting posting parameter.  The reports utilize the point in time tables that are populated and updated during the GL posting processes (stock, work in process and subcontracting).  The output is designed to align with information provided in the general ledger. 

The new reports are executed when the costing mode is “Primary issue method” or “Secondary issue method” and the accounting date option is selected.  The original reports are available when the accounting date is not selected or when the costing mode is not equal to primary or secondary.

The following are some of the new features and options associated with the new reports.

• Ability to specify an end date for any valuation method 
• Automatic inclusion of variance not absorbed
• Option for subtotal by version
• Selection filter and subtotal by accounting code

The summary report provides a beginning balances (based on the start date), activity summary within the date range and ending balance (as of the end date).  The detail report provides the similar information but at a level of detail based on the valuation method and appropriate fields. 

Thanks Rafael.  That is very interesting.  My customer is on the cloud, just an FYI.  He selected primary issue method and entered a date back to 2017, and did not check the accounting date box.  What is misleading is when the report generates, next to the amount column on the report it shows Standard Cost which is the valuation method he is using.  I will have to test this with selecting the accounting date to see if it makes any sense.  The report has significantly higher costs than the standard cost.  

My understanding was to always have the accounting date checked when running these reports for a previous date of today's date. There generally are variables that cause the data output to look confusing and this comes from the STOJOU table and ACCDAT field if populated. 

If you tick the accounting date, only posted transactions will be included in the calculation. So it depends of what you are doing; if your customer is using the stock interface then it is relevant (pay attention that both stock/WIP interface run without error before) but for companies that do not manage the stock interface, this is irrelevant. You can also use this report to do simulation of your current stock value if using a different valuation method, in that case the accounting date is not useful.

Keep in mind, you can enable an activity code (VLT) to enable a secondary valuation method. This is the reason you have the option primary issue method (by default the value posted in your GL using the stock interface) and the secondary issue method. 

Now when you backdate the report, the calculation is very specific and may not match your expectation.
First in 2017, V12 was not released so I the PIT tables aren't populated for this period. If you migrated from previous version, you have to run the related resynch tool.
In addition, if you changed the valuation method during the period (For instance some products move from STD to AVC in 2019), the calculation will likely mixed standard cost with average cost (which is not what you want).

My advice is to run the report at the current date during the period closing process (just before putting the stock status = Closed) and save the result in a dedicated file. The point is to avoid backdating the report which is a long process and can provide different result from what you expect.