dryer plug to two 120VAC 30A ?

No, he doesn't. Think about it a little bit.

Hint: 2 * 110 * 15 is not the same as 220 * 30.

Bad enough you posted an egregiously incorrect response -- didja have to post it three times??

There's NO 60A line there. You have 2 30A lines which cannot be connected together (this would produce a short circuit, actually making 0A available). To get 120V you use ONE how wire and neutral. It would be possible to connect two 30A appliances, but not a 60A one.

I have seen where someone was using a 240V receptacle for holiday lights.

It was an older house, so probably 3-wire. That was supposedly unsafe (current through a bare wire?) but probably not VERY unsafe.

It will function fine in normal use. But the wiring and the outlets in your 120 V strips are likely designed to carry 15 A, while they are "protected" by a breaker that will carry 40 A. This isn't safe in an overload, unless you change the breaker to a two-pole 15 A one.

Dave

The breakers are designed to protect the wiring in the house, not the devices plugged into it. From that perspective, there would be no overload hazard created by this scheme.