They don´t need to double-check data with your local authorities, of course.. it´s all about compliance.. any serious ico should delete files inmidiatelly after review.
None of them delete any info, some of them even sell or use these info.
There are too many fake ICO's, some have only this purpose, to collect ID data and use/sell for various reasons.
No matter what would be the reason.Its still dangerous to give out our personal informations to other people/company/organizations since we dont have the full control of their minds and might end up on those informations to be sold out into illegal market which would really make our identity compromised already and thats why when i find out about KYC rules on an ICO then i easily pass out.