Transmission oil cooler lines bypass question - shady or legit?

So, I just got my 10 speed replaced with an in-house rebuilt unit at a little transmission shop in Fontana California.

Apparently my old one went bad because I lost fluid because my cooler lines are bad.

They could not get a hold of replacement cooler lines, apparently they are back ordered for a week or something.

So they did something that's potentially fishy: plugged and bypassed the cooler lines.

They are telling me:
-That I don't really need them immediately because 10-speeds don't run hot.
-That they bypassed them internally in the transmission so the pump will still circulate.
- But somehow they did it in such a way that I can just put the lines back on and it will flow through the lines automatically without needing to take the transmission apart.
- I don't need to be in a huge hurry to plug them back in, because all that's going to happen is my gear fluid will last half as long as it would otherwise, so like a year instead of two.

All of this seems odd. I'm somewhat inclined to trust them because they do have a one year warranty and I doubt they would make something that would immediately destroy my transmission just so they have to redo it for free...

But it's still odd to me that a transmission can just run internally like that without overheating as they are alleging.

What are your thoughts? Is this a normal procedure or are they BSing me? Can I run this thing until I find time later in the summer to take the lines off of my old truck and put them on myself?

 

Okay, good to know.

The good news for me is that I don't have no 100 K loads, just normal stuff. Heck, I don't even like taking anything over 30,000 pounds, it's just annoying to drive heavy stuff.

The bad news is I don't have any kind of a transmission fluid temp gauge or anything like that. So all I've got to rely on is faith and trying to smell a weird smell if it starts overheating.

Oh, one more weird thing. They did not run an outside hose, they just plugged it with metal screw in plugs. Apparently whatever they did is internal that they do on all their rebuilt transmissions. At least according to them.