--sync option to xdotool windowmap causes flicker

[jojhelfer]

If I run
tdrop -a -A -w 50% -h 100% -x 100% -d 0x0 xterm
the xterm window briefly appears on the left side of the screen before being moved to the right.
However, if I change

		xdotool windowmap --sync "$wid" windowmove "$wid" "$xoff" "$yoff" \
				windowsize "$wid" "$width" "$height" 2> /dev/null

to

		xdotool windowmap "$wid" windowmove "$wid" "$xoff" "$yoff" \
				windowsize "$wid" "$width" "$height" 2> /dev/null

in map_and_reset_geometry (that is, if I remove the --sync), then this flickering does not occur.
(This is line 443 in the version I am currently using, namely commit ef658b2d.)

I would propose simply removing --sync from that line, but perhaps it is there for a good reason which is not affecting me?