Looking back, I think Hunters may have dropped combat if their pet was still attacking while they had Feign Death active. Immediately after exiting Feign Death, you would be entered back in combat. This was necessary for the way that traps worked in vanilla. As I do not have a Hunter and I haven’t played with any L30+ Hunters yet on beta, I’m unsure of the veracity of the claim by the poster. It could have been resisted or there could be other factors at play as well. Until another player who plays Hunter makes a post in the topic (or Blizzard confirms or denies the bug report claim), I don’t know if this is a bug that exists on Classic. Sorry!
If I recollect correctly, you wouldn’t target someone casting on you until the cast was complete. Currently, in Classic, players will automatically target you when you begin casting (like in BFA). So, it may be of slightly less use if this functionality remains the same at release.
I was unable to find any documentation for this in the patch notes. Maybe it was changed at one point to where you were instantly put back into combat? I do remember being able to Feign Death and use traps, but I am having difficulty remembering if I would have my pet with me or not during those times.