rxvt-unicode ebuild has truetype USE flag which in fact enables xft support. rxvt manual clearly says that it's possible to compile rxvt with Xft support and it was surprising for me to see the support enabled by truetype flag which has little to do with it (although certainly it's possible to figure out what it really does contrary to flag description). Since xft USE flag already exists, I suggest to use it instead. I less intrusive but a more confusing workaround would be to improve the local flags description for rxvt-unicode package.
I think we've had this discussion elsewhere recently.
I have no choice but to bump this.
Fixed in 9.15. Thank you for reporting.