Rule 12.5: OR sequence without parentheses not compliant?

[William Forbes]

It is my understanding that Rule 12.5 allows exceptions if the operands are "effectively Boolean"
So you first example is allowed as the expression (start >= end) || (start > 7U) is effectively Boolean.
As indeed is the expression (start > 7U) || (end > 8U)
So which ever way you look at it, it will be allowed under rule 12.5.