The Thief Rogue's Thief's Reflexes feature states:
When you reach 17th level, you have become adept at laying ambushes and quickly escaping danger. You can take two turns during the first round of any combat. You take your first turn at your normal initiative and your second turn at your initiative minus 10. You can't use this feature when you are surprised.
The true polymorph spell states:
[...] Object into Creature. You can turn an object into any kind of creature, as long as the creature's size is no larger than the object's size and the creature's challenge rating is 9 or lower. The creature is friendly to you and your companions. It acts on each of your turns. You decide what action it takes and how it moves. The GM has the creature's statistics and resolves all of its actions and movement.
What happens if the Thief casts true polymorph on an object and turns it into a creature? Does the created creature get an additional turn when the Rogue does?
Note: At least one way a Thief Rogue could cast true polymorph is through feats or multiclassing and using a spell scroll.