I'm an ex RJ-85 pilot, and while I've no idea what they used for their planned diversion, I wouldn't be surprised if this flight was planned as a 're-clearance' operation.
In other words, you plan the flight with somewhere en route as the 'destination'.
When you are about there, you see if you have enough to proceed to your 'diversion', which is really where you wanted to land anyway.
If you have enough gas, you continue- if not, you land and refuel.
I've done this a few times, and in my view while legal, it can turn into a trap for fools.
If you go on to your 'diversion' then you KNOW that you are going to use:
Start and taxi fuel, sector fuel and diversion fuel. Thus you know that you will land with final reserve and maybe some of your contingency fuel, but that's it.
As usual, it will all come out in the wash, but I'd like to think that in these enlightened times, the days of airliners crashing simply because they 'ran out of gas' are behind us. But then, I don't fly in Columbia.....