I'd need to see it in person but I'd call the weld good. What you are seeing is " rotary friction welding " weld flash from the hub and converter cover. One way to test is get a piece of rad hose and some fittings then rig things up to pressurize the converter ( 10 pis is plenty to find a leak with soap )

Hubs can be MIG welded on a fixture or friction welded. Rotary friction welding is where one part is held and the other is rotated, as heat builds the parts are pressed harder together then finally rotation stops and the parts are pressed at an even higher pressure. The machine looks like a metal lathe.

Friction welding is fast and effective on a large scale, but not the kind of thing a converter rebuilder will have. ( I'm specing out a new one at work , pricing is upwards of $ 750,000. )

Your real problem is the pump bushing has failed, look at the two brass lines on the hub. Also look at the galling next to the pump drive slots on the hub. I wonder of the front pump had broken drive tangs at some point and a set of gears was dropped in at some point to get things going again.

When the pump bushing has excessive clearance, the seal rides off center and the increased fluid leakage past the bushing can overwhelm the seal. On some trans ( GM ) it can actually blow the seal out of the pump housing.

I think, that the 722.6 trans needs an alignment tool ( that looks like a converter hub ) to center the pump when the halves are taken apart. If this is the case and that tool was not used, it will cause a pump miss alignment.