Firstly, I am surprised that David Brown has still got a job after all the problems you and other new home buyers have had with Taylor Wimpey on this site and his apparent indifference! I think his latest comment was an indication that he believes that the garages are TOO SMALL to put a car in - similar to the
Persimmon new home owner featured here! Amazing that he thinks this is amusing!
It is true that the bricks may be more absorbant than others available.
I am not sure price would make this more or less likely though! The mortar too could be a weaker mix.
But my guess is that the joints were not fully-filled, both horizontal and vertical.
Unfortunately the only way to check this would be to take out some bricks. You could video the bricklayers working though. Check to see if they are laying frog up for a start and have fully mortared the ends of the bricks, not just 'top and tailing'.
Another cause may be that the bricks were already saturated during the build and could not cope with the extra driving rain. I expect your next issue will be efflorescence of the brickwork. This is caused by salts being drawn out of the brick as it dries out after becoming wet, either during the build (which is most common and likely) or after wet weather. As the water evaporates, it leaves the salt behind, which forms a white, fluffy deposit, that can normally be brushed off. The resulting white deposits are referred to as "efflorescence" in this instance.
Since primary efflorescence brings out salts that are not ordinarily part of the cement stone, it is not a structural, but, rather, an aesthetic concern. Efflorescence can often be removed using phosphoric acid. After application the acid dilution is neutralised with mild diluted detergent, and then well rinsed with water. However, if the source of the water penetration is not addressed (rising damp, leaking rainwater pipes or gutters for example) efflorescence may reappear.