Re: TAB in Eval: prompt in minibuffer?

[Richard M. Stallman]

    BTW, info.el dropped M-TAB in favor of S-TAB.  Unfortunately, this
    makes `Info-prev-reference' inaccessible on ttys where S-TAB is not
    available.  I think info.el, help.el and wid-edit.el should bind both
    S-TAB and M-TAB to the same commands: S-TAB for window environments,
    and M-TAB for ttys.

Could someone please look at the discussion that led to defining
S-TAB in info.el, and see what the motives were?