In Jn 20 Thomas is identifying Jesus as The God
The use of the uppercase in English conveys a meaning that's not present in the Greek text
In Greek (Ancient & Modern) I'm, "the Thomas" when I'm the subject of a sentence, but that shouldn't be understood any differently than we would understand the unadorned name in English.
In other words, "Thomas checked his watch" and "Ο Θωμάς έλεγξε το ρολόι του" mean exactly the same thing. The use of the definite article in Greek shouldn't automatically be understood in either an exclusive or special sense.
Please don't misunderstand. I'm not saying that Thomas was not necessarily acknowledging the Diety of Christ. I'm saying that the grammar does not identify him with the person of God.