What's concerning is that you think this requires a vivid imagination. You ever see a block get window'd Bill? Because I have. Sometimes the rod goes out the side, sometimes it goes out the pan, sometimes it goes out both. Spinning a rod bearing isn't some uber-rare event, and the results are often very messy.
Edit, here's some idiot windowing the block in his BMW M3. Note the fire and resultant oil slick:
To quote one of the spectators in this video: "You can't drive on from here. You need a tow truck." Genius!
That said, a pile-up on the highway requires diligent cooperation from other drivers to happen. Their minimum contributions to be demanded are the conscious negation of any safety distance and igorance of any traffic except the car immedidiately in front of them.
A couple of friends have windowed a block on the Autobahn (because Saab B235R...), one has set his car on fire doing so. No catastrophe ever happened.
On my very first car I have myself had an engine failure* at moderate speed (~180km/h) in moderate traffic, including loss of power steering and brake force amplifier. No big deal: put the car in neutral, put the hazards on and gently coast to the shoulder. If a kid who just got his license half a year before can cope with this, anybody should be able to. (On a narrow, twisty mountain road this would be rather more tricky and the situation would be much more dangerous. But I understand you do not have these in Florida.)
You have one very point though: oil on the tarmac. In a straight line, probably nothing will happen, in a curve that might indeed become dangerous for others. Also not very good for the environment. The fire and the oil spill will negate any environmental benefit from lower fuel consumption.
*The guy who sold me the car a couple of months earlier was super helpful. As he was a high-school-teacher and this happened during the summer holydays, he had some time at hand and just said "get the car to Berlin - I have a donor car that was wrecked in an accident. I can give you the engine for cheap, and I'll show you to get the old one out and the new one in". That was my first engine swap and the first time ever I worked on a car. When we tore the damaged engine down, we found that some sealant had blocked an oil passage. A few weeks prior I had a garage fix an oil leak at the oil filter flange. Turns out they had not used the paper gasket, but liquid sealant, some of which had swelled out to the side into the oil path. Apparently some of this had come lose and wandered through the block.
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