It is linked in the manner it takes place in the same universe as Alien, that much Ridley Scott has confirmed, but the entire production crew are telling the media that is is an 'indirect' prequel with minor nods to the original Alien, to keep fans happy.
In my opinion is just doesnt make any sense to reuse the same Alien Universe if the intention was to only have some indirect references to Alien.
If they wanted a whole new movie they would have made a whole new Universe.