There were 3 extra-inning games on Thursday, all of which ended in the 10th inning.
— ESPN Stats & Info (@ESPNStatsInfo) April 23, 2021
Of the 33 extra-inning games so far this season, 28 of them (85%) ended in the 1st extra frame.
In 2019 (the final season before the runner-on-2nd rule was implemented), it was 44%.