putc vs printf

[Thien-Thi Nguyen]

GNU RCS does not presently use gnulib, but it will in the future.
With that in mind, i have a question inspired by this comment in
the source code:

  /* Output the first character with `putc', not `printf'.
     Otherwise, an SVR4 stdio bug buffers output inefficiently.  */

I don't know what to make of it and am wondering if, when the
transition to gnulib occurs, it's an issue that can be conveniently
glossed over.  Could someone explain this or point me to more info?

thi