Rohan, let's get our terminology straight first.
1) TDE = Tableau Data Extract. This is Tableau's original format for the Extract file.
2) Hyper = Hyper extract. This is a completely new technology that Tableau acquired. It REPLACES the TDE format and is much more efficient.
So, to answer your question, yes, both TDE and Hyper are extract formats but other than that they are completely different technologies. When you say "they're both extracts" it's like saying Ford and Ferrari are both cars so why is there a performance difference?
It does. But in my case, both are hyper extract(embedded data as well as published datasource).