Comment 50 for bug 96676

I also see that the modifyFunctionKeys:2 section of xterm's terminfo seems to be the default.

Looking at xterm's changelog, the default was changed to 2 in Patch #216 - 2006/8/3:
# change default resource modifyFunctionKeys to 2 to avoid sending SS3 with parameters (report by Kalle Olavi Niemitalo).