India’s win in the first Test at Adelaide was prophetic-as it was the first time that India had won the opening Test of a series in Australia. In due course India won in Australia for the first time.
Here is a summary of the opening Tests of all series played by India in Australia:
1947: Lost; lost series 4-0 with 1 draw
1967: Lost, lost series 4-0
1977: Lost, lost series 3-2
1981: Lost, series drawn 1-1 with 1 draw
1985: Drawn, series drawn 0-0 with 3 draws
1991: Lost, lost series 4-0 with 1 draw
1999: Lost, lost series 3-0
2003: Drawn, series drawn 1-1 with 2 draws
2007: Lost, lost series 2-1 with 1 draw
2011: Lost, lost series 4-0
2014: Lost, lost series 2-0 with 2 draws
2018: Won, won series 2-1 with 1 draw.
Also note the draws of 1985 and 2003 which marked the start of a drawn series, although the loss in 1981 also marked a drawn series.
So in 11 of the 12 series, the opening Test was a good indicator of the result of the series.