I've spent some time cleaning this one up and couldn't help but notice that the top tube looks like some sort of electro weld machine technique, while the middle tube (what do you call them) looks hand brazed;

Sweet looking old bike and I like that basket.

Probably done to save time in manufacturing and wonder it if reduces weight too?

This one is made of lead I think.

Really wild, Ben! Do you think the lower tube was after market? Could be both are welded the same way, but someone tried to smooth out the lower one with lead solder... but that doesn't make any sense. Well, what I see doesn't make sense. What do you think it is?

I'm guessing something about the production process made it easier to fit things together this way. I was just reading a Roadmaster ad from '52 that bragged of a "100% electronically welded frame" whatever that means.
I just went and had another look, all the tubes going to the bottom bracket were done like the top tube. The rear fender bridges and seatstays at the seat cluster are done like the middle tube. Maybe the main triangle was done in a machine and the rest was still done by hand at this time.
I stole that basket off my wife's bike 3 weeks ago and she hasn't noticed yet. She never rides that thing. I've been running errands on mine.

Or a repair?

when a frame is manufactured with the resistance welding process they put opposite electrical charges on frame components and jam it together with force when an arc is established, like a giant spot weld. There is on occasion a failure of a joint to properly weld. In those cases, that frame could be run through a fillet brazing process to get it back into the production loop. That would be my guess. Or while the process was being developed they only ERW'd sub assemblies.