As the Mango said....your OK as long as ya don't go trying to do burnouts with a cold transmission. Got to remember that the fluid is coming in under alot of pressure. The Radiator trans coolers are for cars that heat the fluid with the motors coolant, that way when the motor is warm the trans is warm.
Now...., for those of us that don't warm these little cars up properly, just jump in and go, you can run just the aftermarket cooler, but a inline thermostat helps regulate the fluids temp. allowing it to warm up faster, especially with a slippery converter that makes alot of heat.
Ya see, when the trans is cold, so is the motor, the fluids just pumping freely. If there was no restriction in there, the fluid would go thru the cooler too fast and would not allow heat transfer.
Now, on the cars that have the external aftermarket coolers and 3000rpm converters, that slipping creates alot of heat, and that heats the fluid up faster, and those units flow a good amount of fluid, so even though theres little restriction, compared to the stock cooler in the trans, theres more back and forth passages allowing the hot trans fluid to transfer the heat to the coils before being sent back to the trans.
The gap inside there looks tight, they should've put a chamfer on the back side of that bung before welding her in....if they say its fine, guess it passed inspection. I'm a Engine Builder and a fab expert, not a trans guru, but it does look tight to me.