Whether you consider Picked and Registered as On-hand depends on who you are.
If you're a warehouse supervisor responsible for fulfillment of product, then you tend to think of On-hand as including Picked and Registered, since On-hand in your mind is what is available for your purposes. I use the word "available" here loosely, because it is another one of those words you find throughout the AX interface that tends to mean different things.
If you're an accountant responsible for financial reporting, then you tend to think of On-hand without consideration for Picked and Registered, since those quantities do not have an effect on ledger, do not represent a change of ownership of the inventory (like a packing slip represents a delivery to a customer), and as you have noted do not have a Physical date for exactly those reasons.
When I write reports, I tend to show On-hand as Posted + Received - Deducted, and then show Picked and Registered separately in their own buckets. If you don't separate them out, then if you also show inventory value on that same report, it's just confusing because Picked and Registered have no value. Furthermore, if you're a user that cares about Picked and Registered, you probably also care about other buckets like Reserved physical and Reserved ordered, and Available physical, and very quickly it becomes impossible to represent a useful state of inventory for an item with a single number. So, you have to show them all so people can make decisions based on them.
So, having explained all that, to me it makes no sense to talk about Picked, Registered, Reserved, or Available inventory quantities (and of course not value) in the past.
Finally, it's practically impossible to reconstruct a past Picked or Registered quantity because inventory transactions, as they are split and summed, change state from On order, to Picked, to Delivered, to Sold. The Delivered state leaves a nice audit trail in the form of a Physical date and a Physical voucher, and the Sold state does the same, and because of this clean audit trail these effects can be "reversed" to achieve point in time reporting. But what state is left for Picked? Can you even tell if an inventory transaction ever spent time in the Picked state? How do you reconstruct an inventory transaction that went from On order, to Picked, back to On order, and then gets deleted entirely because the Sales order was canceled having never been delivered? What if you pick, un-pick, and pick again, does the single Picked date field reflect that?
The only practical answer is to entirely ignore Picked and Registered for point in time reporting.
