Well, it can be used that way. But you have to answer all the prompts correctly. It is good to turn on echo so you can see what you type.
But it won't do file transfers between a TI and other computers. Back when it came out, there was only one standard file transfer protocol that I remember, called Kermit.
So TI rolled their own.
Yes, back in the day the TE-II was very exciting, not just for the speech. TI's were one of the first to have graphic BBSes, with music and speech! I remember logging onto one back in '83 called Texas Instruments Telecommunications System (Sysop was Blaine Richard) in Apopka, FL. He had a large collection of stuff taking advantage of the TE-II.
But I think you'd find 300baud to be very limiting today, except for local hook-ups.