Power supplies don't push current, you can't push more current than a load will take and you can't receive more current than a supply will generate.
Just because a PSU claims 600W doesn't mean you can always get that 600W out of it. While its true 60V @ 10A is 600W and 30V @ 20A is 600W as well, and logic would dictate that at 2.2V you should be able to get 272A for 600W, the simple fact is very few PSU's are designed to crank out that kind of amperage at that low of a voltage. Most of them aren't made with that consideration in mind.
Think of PSU's are either current limiters or voltage limiters. If you cap the voltage (in CV mode) then hook up the load, the amount of current that flows through the circuit will be capped at either what the supply can generate or what the load can support. It will stop at which ever one it hits first. If you have a 12V supply and add a 1ohm load to it, the most current that you can see through it is 12A assuming the supply is good for that voltage and current combination. Cranking up the "current" knob on the PSU won't make it push more current through that load without something else changing. If you want to increase it to 15A through that 1ohm load then the voltage across it will need to be increased to 15V.
When we set up laser diode drivers we set the current we would like to see, it sets a limit or a cap on the maximum amount of current that can flow. Because voltage and current are tied together, the driver (behind the scenes and without any intervention from the user) adjusts the voltage output accordingly to be appropriate for the load. Laser diodes differ from traditional resistors in that their resistance change across a given range but the same laws still apply.
