I am trying do describe the difference again.
I mean, isn’t it obvious.
as:Object
You just replace “as:” by the URL – now click
https://www.w3.org/ns/activitystreamsObject → “Document not found”
ActivityStreams 2.0 Terms → Yay
(https://www.w3.org/ns/activitystreams#Object - cause this software parsed the Link already)
I mean, it doesn’t make a difference for JSON-LD machine-consumers, only for people.
But then, I think it makes sense to use the one which resolves to valid URLs for e.g. JSON-LD and HTML/RDFa, which is
https://www.w3.org/ns/activitystreams#