I thought TfL allowed a few minutes [<5?] to allow for disinclination to travel due to delay etc.
Recently at London City Airport DLR, I had been waiting for 7 p.m. (for cheaper fares) but discovered the lower level entrance and forgot I was waiting for 7 p.m.
I tapped out again and wasn't charged for the first pair of taps.
I started my journey at the high level entrance after 7 p.m.
Actually, the correct start of journey at 19:01 was amalgamated with the in/out taps and the journey started at the pink reader at Canada Water during the journey.
Correct fare was still paid.
Tuesday 15th March 2022
Fare for this journey: £0.00
18:56
London City Airport
18:57
London City Airport
19:01
London City Airport
****
This also worked a few years ago at a fully barriered station (Harrow & Wealdstone) when I entered just before 7 p.m. and then realised train was delayed.
I was able to exit without charge and re-enter after 7 p.m.