It all looks like pretty straight forward to me!
It is an offence to plan a flight such that the mandated fixed reserve will not remain intact.
It is an offence to not divert (while the opportunity still exists to do so) when the PIC becomes aware that continuing to the original destination will mean landing with the reserve not intact.
It is NOT an offence having satisfied the requirements above, and at a point beyond the latest point to make a safe diversion, that unforseen circumstances cause the flight to be completed with less than the required reserve.
Examples of Unforeseen circumstances;
Winds stronger than forecast (should have planned some variable reserve!)
Unforeseen traffic or weather holding at the destination (effective after the latest safe point to divert)
Aircraft system issue that delays the landing at the destination (eg landing gear problem)
Any other issue that delays the landing beyond the PIC's control!