My understanding is there is actually nothing to "sign" for a transfer, they just enroll in school and start classes. Not all transfers enter in the spring, so the ones who will join the class in summer semester technically will not have "signed" yet. I guess that leaves the door open for them to potentially go somewhere else, but not sure because there is nothing a transfer actually "signs" when they commit until they enroll and register.
But as a side note... I can verify the following that say "not yet signed" are all enrolled at GT for Spring:
Jordan Brown
Abdul Janneh
Christian Leary
Etinosa Reuben
The only transfer not in yet is Seither, but by all accounts I expect he will be registered and in classes tomorrow (today is a holiday). Chase Lane is also not officially in yet, but it was known he is finishing out his spring semester at Texas A&M and will join the class in the Summer.