Reverification is part if new routine process that amazon is adopting worldwide and on all accounts, not just new accounts.This is because as the worlds biggest online retail marketplace amazon has to follow rules set by the governments. US, EU , UK all require online marketplaces to collect and maintain records of sellers identifications, individuals as well as companies.
I have clients in US who are having amazon seller accounts since many years and they are USA citizens, still they are asked to reverify....and they simply comply....as long as the seller is complying to the rules of the land, there should be no concern or worry....problem is most of the sellers who "think" that they are in compliance , are not even properly aware of the rules of setting up business...and hence end up losing money
..and time and effort.