Attaching / detaching lead from far away in creative client-server desync

When I was testing the new rope/leash, it appeared like I was using one, but it was not having any effect on the horse (it was not pulled by the rope), and it did not break when far away from the mob.
When I tried to detach it, it actually attached it (behaved as intended).
I think it was showing but not technically attached to the horse.

(Sorry for possible English mistakes )