"Below V1, in the event of a critical failure the take off MUST be aborted"
"Above V1, in the event of a critical failure the take off SHOULD be continued"
I believe 'should' is correctly there because the PIC in command SHOULD continue the takeoff unless it is considered to be an unflyable malfunction, and therefore a greater emergency exists.
This last comment does appear in many SOPs you will find.
Cheers.