Comment 10 for bug 1646034

For the tilde expansion, the code has not changed between gtk2 and gtk3. The line in question is in optionparse.py:
os.chdir(os.path.expanduser(options.working_directory))

And this line is from way, way back in the beginning of 2009, (though originally in the main script, moving to optionparse.py in 2010.) libc also provides for tilde expansion:
https://www.gnu.org/software/libc/manual/html_node/Tilde-Expansion.html#Tilde-Expansion
So it's not *exclusive* to bash, and I don't believe we are doing anything wrong by expanding it ourselves. We just provide a little extra utility over others ;-)

As to the original complaint. The optionparse.py file has not changed a single line (bar the 1st shebang line to spec python2) between the gtk2 and gtk3 versions. At no stage (recently at least) has Terminator accepted non-option arguments. So passing a path on its own will not work, and should never have worked. You will get the message:
terminator: error: Additional unexpected arguments found: ['/usr']

For me Thunar works as expected with two minor wrinkles.
1. When DBus is active the folder requested is ignored for secondary windows (the first is OK), and the new secondary windows inherit the directory of the Terminator processes current working directory. We need to fix it so that options passed with DBus active do not get ignored.
2. When DBus is active the first terminator window opens in front and gets focus. Secondary windows (i.e. ones using DBus to launch) open behind Thunar, and do not get focus.

Nautilus with the addon for opening a folder in a terminal on the other hand, completely ignores my preferred terminal, and hard launches gnome-terminal!