Chris McNulty, Henrik Nordtorp, Null Null, Rob Franco, Michael Dickerson & Dev Chaudhari re "Document IDs are constant only if you move within a site collection".
I was thrilled when the new 'Move' function was finally released. However, after testing a few moves, what's the use of a 'Move' function if previously shared links no longer work? Microsoft did you really think that companies using your online SharePoint product would not have the need to move documents from Site Collection to Site Collection without keeping the document's persistent link?
We, like Michael Dickerson, Dev Chaudhari and Null Null, reference documents stored in SharePoint within 100,000+ of other documents stored in SharePoint. Previously created links that have been shared and referenced in Process, Policy and Procedures Documents and Templates are used across the company including our intranet information systems so we need these to continue to work wherever the document moves in a SharePoint Online Tenant Collection.
For Microsoft to design an online SharePoint system with a Document ID that is not a true GUID (Globally Unique Identifier). For certain users, that's a backward step and for some, dare I say it, a huge design flaw.