I went through the old handbooks to see when this policy went in place. The first instance I found was actually in the 1960 handbook. It says:
So, the 1 year wait only affects those who can get sealed in the temple but refuse it. The 1963 handbook is similar.
The 1968 handbook is when the rule affects all civil marriages:
And, interestingly, the 1976 handbook is even stricter:
So, if you get civilly married, you can't do any temple ordinances except baptisms and confirmations. No washings, annointings, or sealings for the dead.