It reflects a change in IPO filing law. Quoting Wikipedia: "Under the JOBS Act, it has been possible since April 2012 for "emerging growth companies" to file a

It reflects a change in IPO filing law. Quoting Wikipedia: "Under the JOBS Act, it has been possible since April 2012 for "emerging growth companies" to file a Form S-1 on a confidential basis, only making the contents public 21 days prior to the road show for the IPO." With many IPO filings, the financial docs are immediately available to review. Because Snap filed confidentially, we are not given access to these docs until shortly before the actual sale of the IPO shares.