That is correct but having an oil cooler gives you sort of an extra half a chance to catch something that is going wrong. In most cases, that extra chance is all you need to get home with a leaked radiator pipe or a fan problem etc and spare yourself a steaming hood and a cracked head.
Basically any turbo diesel engine is a ticking time bomb when you spike up diesel timing, delivery and / or turbo pressure without any other upgrades. The 2LT being a small engine with a relatively big turbo has all that much more rope to hang yourself with. You will come across very few 2LTEs with head crack issues as there is little tinkering that can be done with the electronic pump. On the mechanical pumps, even when diesel pump timing / fuelling is calibrated to normal / factory standards by our local diesel lab techs & mechanics, it actually is at moderate to sufficiently advanced levels. Add an AC and our summer ambient temps and going for a motorway drive pushing 130 kmph is quite a nice a recipe for disaster.
In the end I would think that along with everything above, the best prevention for a cracked head on a 2LT is to ensure that the engine timing and fuelling is at factory standards, which in local lingo normally means to retard the damn thing. You don't lose all that much power and acceleration and it will help you make the dinosaur last a while longer! All the best!