Yes you're right - I don't use multi algo so was going on the description of how to set it up and didn't spot that each line had a different port number, that does make more senses than trying to detect what algo is being used!
The Multi-algo port detects which algo you are using and routes you to the correct pool.
each algo have their own port btw.
This is how I see it:
The pool "kicks you" out (by not giving you work) until you start mining the "most profitable" algo from this list (its a loop):
:start
EthDcrMiner64.exe -epool us-east.ethash-hub.miningpoolhub.com:12020 -ewal username.workername -eworker username.workername -esm 3 -epsw x -allcoins 1 -retrydelay -1
#ethminer --farm-retries 0 -G -S us-east.ethash-hub.miningpoolhub.com:12020 -O username.workername:x -FS exit
ccminer -r 0 -a groestl -o stratum+tcp://hub.miningpoolhub.com:12004 -u username.workername -p x
ccminer -r 0 -a myr-gr -o stratum+tcp://hub.miningpoolhub.com:12005 -u username.workername -p x
ccminer -r 0 -a x11 -o stratum+tcp://hub.miningpoolhub.com:12007 -u username.workername -p x
ccminer -r 0 -a x13 -o stratum+tcp://hub.miningpoolhub.com:12008 -u username.workername -p x
ccminer -r 0 -a x15 -o stratum+tcp://hub.miningpoolhub.com:12009 -u username.workername -p x
ccminer -r 0 -a neoscrypt -o stratum+tcp://hub.miningpoolhub.com:12012 -u username.workername -p x
ccminer -r 0 -a qubit -o stratum+tcp://hub.miningpoolhub.com:12014 -u username.workername -p x
ccminer -r 0 -a quark -o stratum+tcp://hub.miningpoolhub.com:12015 -u username.workername -p x
ccminer -r 0 -a skein -o stratum+tcp://hub.miningpoolhub.com:12016 -u username.workername -p x
ccminer -r 0 -a lyra2v2 -o stratum+tcp://hub.miningpoolhub.com:12018 -u username.workername -p x
ccminer -r 0 -a vanilla -o stratum+tcp://hub.miningpoolhub.com:12019 -u username.workername -p x
timeout 1
goto start