I get the impression fighters know precisely when the round is going to end - based on the sound that comes at 10 seconds, the screaming of their coaches/teammates, and then the actual bell itself. In the first incident at the end of round 2, both fighters were "relaxing" in the clinch with full knowledge the bell was seconds away. Having just watched it again, De Randamie knew exactly what she was doing. She literally hit Holm nearly an entire second after the bell. That is completely unacceptable. Both De Randamie and the ref are at fault - one for the after the bell punch and the other for not giving a warning.
The 2nd one was not as pronounced but when factored in from the incident in the previous round, it was enough for a point deduction. Horrible reffing.