They don't automatically tell the registered keeper, but the registered keeper has the right to ask them for a copy of the form from any request. Given that the information is supplied by post, you can assume that the address is in some way linked to the person asking for the info. Giving information out to "anyone who requests it with due cause" is slightly different from how they handle the car park companies as I understand it. Therefore the "thief" needs to provide a credible story to go with it. Obviously if that turns out to be made up then there is the start of a case, and somewhere for the police to start looking - and probably a separate offence (which the form suggests carries a fine of upto £5000).
If I thought this was likely I'd be asking DVLA for any forms submitted for my car. Then if the reasons were dodgy I would pass them on to the police with the suggestion. Obviously if there are a cluster of thefts and they involve DVLA requests there is a pattern, and if the idiot thief had them all sent to the same address their is the start of a circumstantial case.
In reality I think it is too drawn out a process for the average thief.
(1) They need to be able to spot high value bikes when on the move.
(2) Trail centres (ie. locations with a high density of such bikes) attract people from a wide radius. A thief "working Glentress" might get hits from vehicles from glasgow, to dundee, and newcastle. That is a big patch for a petty crim to cover.
(3) Company vehicles will not usually be registered to the house.
(4) The best bikes might not be the driver of the car (eg. if I drive with my mate's £3500 carbon dream machine on the roof, alongside my bike - the thief will be dissapointed to break into mine, and probably put his back out lifting the heavy bugger of a bike).
(5) You get no indication of likely security, e.g. shed, garage, attached to house or separate, overlooked or rural, bikes inside the house, alarm etc.
All together the odds of getting an "easy" steal, of a high value bike by matching number plates is not that good. To be making a living from nicking bikes you would need to put in a lot of V888 forms which would likely attract some DVLA attention, and certainly make it harder to cover your tracks.