It's perfecly fine to do btests from router, as long as you keep watch on the router CPU usage to make sure you not limited by that.
So btesting from each hop to the next, be it router, AP, outdoor link, etc. is always good practice. If router is used in SOHO environment then there simply is no other router behind that to use for btesting (unless you use one of the free internet btest servers). But most routerboards can easily run btest at full wire speed (100MBit/s). If you are testing GigE or faster interfaces, you have to check first if CPU usage isn't limiting factor... but on newer HW like RB4011 that's fine too.
Overall I don't see anything wrong with topic author's question or practice... what I do see is reply from Normis that's not really helpful, not really answering any questions, just criticizing gemesif and avoiding the real questions as usual...
If you have android phone and notebook, you can connect the NB using cable to router, run iperf server on it and then use GE tools on android phone for testing (it does have iperf client in it) to test wifi connection. As you can see state of btest support on other platforms is rather sad.... so we have to use workarounds like this.