1 The retired out law in cricket
As per the ICC's rules a batter can get himself retired out in T20 cricket, but he/she will have to inform the umpire about the decision.
According to MCC Law 25.4.3, "if a batter retires for any reason other than as in 25.4.2 (retires because of illness, injury or any other unavoidable cause), the innings of that batter may be resumed only with the consent of the opposing captain. If for any reason his/her innings is not resumed, that batter is to be recorded as 'Retired - out’."
2 List of batsmen retired out in T20
There are only four batters, including Ashwin, have been retired out in the T20s. The list has Shahid Afridi of Pakistan, Sonam Tobgay of Bhutan and Sunzamul Islam.
Retired out batsmen in T20s
Shahid Afridi - Pakistanis vs Northants Tour Match, 2010
R Ashwin - Rajasthan Royals vs Lucknow Super Giants IPL 2022
Sonam Tobgay - Bhutan vs Maldives T20I, 2010
Sunzamul Islam - Cumilla Warriors vs Chattogram Challengers, Bangladesh Premier League, 2019.
3. Retired out batsmen in Test cricket
In the nearly hundred and a half decade of Test cricket only two batsmen have been recorded as retired out. It happened in 2001 in a Test match between Sri Lanka and Bangladesh. Lankan skipper Marvan Atapattu called back Sanath Jayasuriya after scoring a double hundred. In the same match, Mahela Jayawardene also retired out after making a 150.
4 Ashwin, a rule follower
While opting to retire out, Ashwin followed the MCC rule to the T in an IPL match. Ashwin has done that before too as in following the rule. Remember Mankading (no longer an official term) or running out the non-striker for backing up too far. It happened in IPL 2019 when Ashwin, then playing for Kings XI Punjab, ran out Buttler of Rajasthan Royals, batting on 69.
Rajasthan was chasing 185 and were placed good at 108 for 2 but the dismissal of Buttler triggered a collapse and the RR ended up at 170 for 9 to succumb to a 14-run defeat. Later, the MCC accepted 'Mankading’ as an official mode of dismissal and removed the stigma of unprofessionalism on it.
It may be a quirk of fate that Ashwin and Buttler are now playing for the same in Rajasthan Royals. But this time the Royals was benefitted by the rule awareness of Ashwin than being at the receiving end of it.