This was part of Public Law 97-248 that changed annuity and insurance distributions from coming first from your investment in the contract for amounts invested before that August 14, 1982 to coming first from taxable earnings on amounts invested after on or after August 14, 1982.
See page 5 of IRS Pub 575: https://www.irs.gov/pub/irs-pdf/p575.pdf
However, if you cashed in the entire policy, this difference in what portion comes out first does not matter since it all was distributed. In this case the insurance company is apparently then not issuing a Form 1099-R simply because the amount of investment remaining in the contract was simply more that what was paid back out, and under those circumstances no reporting is required on a Form 1099-R or on your tax return.
