If you have earned the right to pre-use the Kill-tracker Ghost because you purchased a pre-order that included it as a bonus, it may be added to your general drop list and may be received from certain Engrams. However, if you did not unlock it through Pre-order bonus entry, then you'll not be able to receive it from Engrams until after December 6th, 2017, when it (along with Coldheart) leaves the pre-order exclusive zone and enters the general random drop list for everyone and may drop from their respective Engrams. So you may receive the Kill-tracker Ghost from Engrams only if you actually have the right to use it now, but if you did, you'd have received it from the Shaxx once already and can purchase it multiple times through that without needing to use Engram rewards. If you didn't get the pre-order bonus that gives it to you, though, you'll be able to receive it in early December. So the answer is "Yes, it may be true, but only if you already have the right to use it early, otherwise, not until December 6th."