Yep, there is also a lot of discussion about it not working that way.
As I said, I’ve not seen any evidence that what you quoted is correct, and there are a lot of people who have the same issue. Whether that was intended or not doesn’t seem to be clear, as I am not sure Blizz has ever addressed it.
Maybe I’m misunderstanding you, but what I’ve quoted is straight from the 2.3.0 Patch Notes. And if Blizzard has changed this, they would have put that change in a later Patch Notes Blog.
Therefore, it’s not working as intended. And that makes it a bug.
If it’s a bug, then it should affect any and all plans. But it doesn’t. All the basic plans drop as per the patch notes. It is only the “end game” plans that don’t have a guaranteed drop. That makes it seem that it is on purpose.
I am aware of those patch notes, but as I said, I’ve not seen this being true, and judging by the number of complaints, it seems that either the patch notes are wrong, or they are being read wrong.
Okay. I concede. 
I’m not getting the Plans, but it hasn’t stopped me. I’m just playing my builds as I did before we got the new Plans. 
Of course, it would be nice for someone at Blizzard to state once and for all whether this is intentional or not. It would at least quiet down the conspiracy theories.
Edit:
OK, so we finally got official word on this. No bug
Hi : perhaps we should tell people to post all their bugs onto the General Discussion forum 
Right. I can see it now:
This is not a bug. Please move your thread to… blah, blah, blah.
(Time to type up a prepared response for copy/paste in all the continuing bug report threads. 
)
The forum should post a standard reply to these topics automatically. 
Of course, move them to GD as well.
I came here With the same problem, but thought I’d try what was suggested. I lowered from T16 to master, restarted the game (in case there as an update) loaded act 5 and got Trimmings in my first bounty.
yeah same here did bounties on t9 until no more plans dropped and then some more to be sure
startet to search for bugs/etc and found this thread
lowered the difficulty to master and the first bounty gave me the 2 missing plans