lol, calm down mr white knight, you are blowing this way out of proportion. You are making it sound like this is a big gamebreaking bug that sinister players are taking advantage of to gain a huge advantage over poor inocent players

Remeber, we are only talking about animals Slowly gaining some stars while in the tradecentre (and remember, they do not gain this star rating faster than if they were out in the habitat, and it only works if you are online In that zoo)
Stress doesn't apply in the tradecentre. It doesn't go up or down, and I think the only reason the notification don't go away when you put it in the tradecentre, is that if you are treating your animals poorly, you can't just put them in the tradecentre to make the problem go away (like protestors). Just fix the problems with the animals before putting them in the tradecenter and there won't be a problem

(About the growth thing, not sure what that is, never noticed it).
You are wrong about the chellenges not beeing able to be completed in "normal setting" what ever you mean by that. Yes, it's true that some animals, like flamingos, don't seem to be able to reach 5 stars in their lifetime, no matter if they have 100% longevity, but we haven't had a "release 5 star flamingos" challenge. The ostrich challenge were in no way Impossible if you had your animals in their habitat (sure, maybe if you had ostriches with low longevity, 0-33%, but come on, ostriches are abundant in the market and finding one male and one female at 100% longevity is neither hard or expencive!, and those two can produce more than enough babys for the challenge)
Yes, I use the tradecentre in the challenges, since I usually have hundreds of animals in my tradecentre due to the breeding programs, but I also use the habitats. And for all challenges, I have released many animals that were out in the zoo, so saying that it's impossible for "normal" players is just wrong. It all comes down to how much time and effort you are willing to put down.
My point about other things beeing considered "cheating" according to you, is that you seem to think that the challenges are somehow "unfair" because some people release animals from their tradecentre, something that not all players are aware of is possible. Well, some people don't take "advantage" of the fact that you can create a new zoo just for the challenge and by doing so get a huge advantage, since they can just focus on the species for the challenge and don't have to worry about money as they just delete the zoo after the challenge is done.
And to say that knowing about the challenge many days ahead (the connected community page) is not an advantage is just ignorant. Of course it it a huge advantage over people who doesn't know the page exist, Even when it comes to star rating challenges.
You claim that the star rating challenges aren't affected by knowing the challenge in advance. Eh, that is simply not true. Lets take the ostrich challenge for example. You can buy/breed a bunch of ostriches the week before, put them in a zoo, set the speed to max, wait for them to gain 3 stars, put them back in the tradecentre, then log in as soon as the challenge starts and release all of them. So you can prepare for that just as you would a breeding challenge...
Oh, and you do realise that the "prepare a zoo then just leave it running" works just as well with the animals in the habitat, right?

You prepare by getting some animals with 100% longevity (or just breed them, it's not that hard), put the babys in habitats and give them all they need and then you just leave the game running. Come back before the animal dies or becomes infertile (you can very easily estimate the time for this, since you know that a year is 18min and you know how old the animals can get).
With the ostriches this was even more easy, as you can leave the zoo running for over 15 hours without the animals dying of old age (if you want to put your poor pc thru that).