DID Document Metadata `created` property

[wip-abramson]

The spec states

created
DID document metadata SHOULD include a created property to indicate the timestamp of the Create operation. The value of the property MUST be a string formatted as an XML Datetime normalized to UTC 00:00:00 and without sub-second decimal precision. For example: 2020-12-20T19:17:47Z.

I wonder about this "SHOULD include a created property to indicate the timestamp of the Create operation". How many DID methods are there that can provide this value in a in a reliable manner? Not just self attested by the DID controller?