15.1 update failed repeatedly on my Intel MBP 13", both from system settings and using "softwareupdate --fetch-full-installer --full-installer-version 15.1". I even got a kernel panic, something I haven't seen since OSX 10.0. Booting into Safemode and doing update finally succeeded. But I guess Writing Tools is M-series processors only! I would not have worked so hard had I known.