I don't know about OP's intention, but I always took and intended "someone you grab a beer with after work" to mean something along the lines of "close acquaint

I don't know about OP's intention, but I always took and intended "someone you grab a beer with after work" to mean something along the lines of "close acquaintance" or "casual friend". Someone you more than incidentally hang out with via group meets or mutual friends, but not quite someone you would invite to a small intimate event. It doesn't necessarily imply co-workers, but usually that's where that sort of friendship develops; given forced proximity.