Note that scrl and scroll may be macros.
The SVr4 documentation says that the optimization of physically scrolling immediately if the scroll region is the entire screen "is" performed, not "may be" performed. This implementation deliberately does not guarantee that this will occur, to leave open the possibility of smarter optimization of multiple scroll actions on the next update.
Neither the SVr4 nor the XSI documentation specify whether the current attribute or current color-pair of blanks generated by the scroll function is zeroed. Under this implementation it is.
The XSI Curses standard, Issue 4 describes these functions.