I just crossposted something using Thunder and another user let me know that my crosspost did not show that the other post was the original.
See here: https://lemmy.ca/comment/11901004
Not sure how that can happen but seems like a bug in Thunder then?
No. Thats how all cross-posts on lemmy work.
The “cross-posted from” does nothing, and is redundant.
Any client with proper cross-post metadata support will link to all other posts with the same URL in the same way.