The man cannot channel with enough strength to crush a rock, but he can match Rand in making a Gateway. If it was as simple as flow affinity then Egwene would be making monster gateways too. In addition Androl clearly shows an ability with the actual weave that nearly no one else does. He's innovating with it to make it more useful for his lack of strength.

Also, simple Flow affinity is reliant on Strength. That just makes something easier for a channeler to control. Androl is displaying an ability that only a Talent can explain. He is performing a Weave with far less Power than he should be able to ... By your definition Berowin should also be able to make huge gateways and Androl should be able to Shield Rand ... If it was just affinity to Spirit that is.