I love the picture of the bike in the trunk! All I can think about is gas pouring out of the carb, oil drippings, and mud all over the place. Not where I'd lay a bike down. There also looks to be no room left over to put the detached front end in.
Actually, Honda had that pretty well covered. First off, ST70 models were road-oriented than the CT70 models we're more familiar with. Draining the carb is pretty easy with the original carb, there's a thumbscrew drain needle. The tank should seal pretty well, even the plastic tank, though it would be simple enough to pour the gas out, especially with the front end removed. Crankcase oil leakage should be a non-issue as long as the motor isn't upside-down, there's only a fraction of a quart, not enough to reach the intermal oil breather baffle, let alone pour out through it. Granted, the front end would have been relegated to the back seat of that econobox coupe...but then Japanese people are known for their incredible tolerance for tight spaces. With the bars folded down, I doubt the couple in the ad would have felt any more claustrophobic than usual. Beside, they're only pretending for the camera
I've seen very few White Daxes and nearly all of them had the non-demountable front end. As much as I'm into more practical, modified, bikes that can cope with traffic and won't lose collector value if ridden, this one's a keeper unless someone offered serious cash.