Thanks for the clarification.
Why have you got the embed truncate site setting enabled in Discourse? I’m just a bit confused as you mention you’ve disabled it, but you also say your problem is
The embed truncate setting is there partly for this very reason. It means the user will only see a partial excerpt of the post on Discourse itself.
Could you just explain a bit more what specific user behavior you’re trying to avoid, and what specific user behavior you’re trying to encourage.