Both those statements have the same meaning in Flight Safety terms - as they approached the Mull they should have been at or above Safety Altitude until they were unequivocably certain that the en route weather ahead was suitable for low level flight at high speed.
- which as you well know would have meant abandoning the trip and returning to Belfast due to a/c limitations NOT FORGETTING the fact that if they had been '
at or above Safety Altitude' they would have had NO way of knowing what the 'en route weather ahead was' since they would have been IMC. Based on your analysis (which renders the flight un-flyable), why was the authorising officer not charged with negligence?
Has it occurred to you that they might have been
unequivocably certain that the en route weather ahead was suitable for low level flight at high speed on their
planned route?
Define 'vicinity' too, while/if you are answering.