Why does more fuel equal more safety?
More fuel only means extended holding and a greater choice of in-flight planned destination alternates. It may increase your chances of landing at your planned destination, only because you can hold for longer than those on "minimum fuel". Where the 'extra' safety comes from is a mystery, all the time we have control over where we point the aircraft and up to the minute information about airfield weather, it is not compromised.
More fuel also increases your landing speeds, LDR, brake temperatures on arrival plus en-route fuel burn. Over the last ten years I've been flying on our minimum fuel policy and I've not had to divert nor arrived on minimum holding fuel. I've been within minutes of doing so...
Whether the company want you to divert or not is a different matter. They do this by the way the way they write their policies on carrying additional fuel. My company encourage me to fly with the barest minimum fuel, but only ask me to tick a box if I want more. But when faced with pure grot, I'll give then a call (their phone). They'll use their "skill and judgement" and say how much extra they want me to carry want OR and this is a big "or", they'll ask you to go and divert if you have to. And if during this call, I want more fuel, then I'll be given it. Even if that means we off-load passengers. Either way they'll pay me and look after the passengers whatever the outcome.
What is really important is that as soon as it appears you'll be landing with less than 30 minutes (of whatever your prescribed minimum) of fuel, you declare an emergency (aka "mayday"). If the RYR guys were in that position, then they did their jobs.