Just because it's labeled as one, doesn't mean it works at all like one. From what i've read and researched, it doesn't function anything like a traditional Tom Thumb bit.
It may be marketed as one, but since it works in a completely different way, it isn't one. I can say that with 99% certainty after researching the matter further. It peaked my interest that Tractor Supply (Or rather, that particular manufacturer) had it labeled as a Tom Thumb. Just another example of ignorance and (of?) marketing. I guess it's better than labeling a true Tom thumb as something else.
Not all jointed Curb bits are Tom Thumbs, but it would seem from what i'm gathering that practically anything with a jointed mouthpiece and shanks are labeled as Tom Thumbs for the sake of marketing. The truth of the matter is, this particular bit is not going to function anything like a tom thumb bit, therefore I am going to say it's not a Tom Thumb, whether or not the manufacturer wants to call it one.
At any rate, I used it on her today and she went well in it. It gave her something new to think about, and it didn't slide through her mouth (obviously) so that was great! She did have her first EVER try at being a bucking bronco, but I think that was because she was given her head at the canter and has nothing to do with the bit