Yeah, the turning-things-to-lava seems to be a thing of ages past... I've honestly never seen it happen, come to think of it. Maybe it disappeared even with the reactor rework in 1.3, who knows?
It's just that, up until now we didn't have that much reason to build high heat reactors. The occasional breeder liked to run hot, sure, but even the smallest ones were fast enough to support all but the most exotic of reactor setups, so there was never really a reason to push the boundaries that everyone thought existed.