Unfortunately it will not impact their business much at least not for a while. Most sales will come from the assembly contractors or people paying over the odds for their ironmongery. So they likely make their money on big items that are easy to find or assemblers putting in large orders directly to them without going through the site.
But those assemblers are employing people with little more skill than the people working at RS (oh how I want to laugh when I ring up to complain about the site and some ditzy customer service agent says that they can help me find the part I want). So assemblers like to have BOM's with distributor stock numbers, Newbury have become champs at this when they wrote in stating that a micrel LDO was now obsolete. This was because they had a farnell number. Farnell in their infinite wisdom set the stock of these regulators to 0 and stated that they were obsolete. Then they duplicated the listing with the live stock and put Microchip down as the manufacturer as they bought micrell out. So it took me seconds to find the replacement for them by simply searching for the manufacturers part number rather than the stock code.
So RS will in the future be loosing sales when products being made now disappear and we are making products designed at a time when the RS website was unusable so other stockists numbers are on the BOM. Personally I refuse to put stock codes on my BOM's, it's insane to reference a number that could be changed in years to come. I always put the MPN and go to some lengths to make sure that it is the correct full number baring the TP or R or whatever they put or i will just put all the options.
I just had an LT part that has the tape and reel suffix before the lead free suffix
so I can't have an MPN that just has some character's missing off the end, the extra characters appear to have more significance than they do. But I try.....