Not only LSWS, by default, Apache can only have 255 concurrent connections, but they still be able to survive on the 1000 concurrent level test.
That is true that at give time, Standand Edition can have 300 concurrent connections at most. However, it can more clients when it does not keep connections alive. LSWS will changes to non-keepalive mode when total concurrent connections reach certain level. That's why it can successfully pass the test like "ab -n xxxxx -c 1000 -k ..." with most requests non-keepalive.
ApacheBench does think the concurrent level is at 1000. :-)