You should be able to amend the reversal date of the BOM build when reversing it. A date field shows up, but is greyed out and automatically populated with today's date. This causes issues when trying to do a retrospective Stock Valuation because the components of the build are counted as well as the built product. For example, a BOM Build is done on 27/02/2018, and reversed on the 01/03/2018. If you run a stock valuation dated the 28/02/2018, it'll count the built product that was created on the 27/02/2018, as well as the components that were a part of it because it's now been reversed.
One the reversal process all component movements are the same date as the original build but the top level item show the movement as the date of the reversal. Just having this date the same as the original build would be so useful.