S13 SR20DET Weird stock radiator hose line going.. where??

[goodlucksilvia]

So I've had my s13 for about a month now, bought it as stock as can be... still had the original plastic oem radiator from what I can tell, which finally gave out and cracked when I was driving. The car is fine, temps read normal and I pulled over as soon as soon as I smelled the coolant leaking. There were only minor leaks so I'm lucky I caught it right when I did. So I'm now working on replacing the water pump, thermostat, temp sensor, hoses, and radiator. When I was taking the stock radiator back out I noticed a hose line at the bottom that looped back to itself which made no sense at all. I'm new to this stuff, I'm still learning things about my car and cars in general, but I knew there was something weird about it. When I removed the hose, oil came out. There isn't oil leaking anywhere else, and there definitely wasn't oil anywhere in any of the coolant I drained. The car was serviced recently prior to when I bought it, and the motor has been running great. It seems that the line doesn't even go into the radiator itself or might be clogged or something, because if that were the case then the oil in the hose would have came out along with when I drained the coolant. The new aluminum koyorad radiator I bought doesn't have these same lines/openings as the stock radiator, but has mounting brackets there instead. Koyo says its supposed to be a direct fit like the factory one, and I know for sure I bought the right one specified for the s13 SR20DET.

I'm worried there's maybe something I might be missing or unaware of so I thought I would ask around on here, trying to figure out if its ok for me to just ignore that hose line and continue with putting in the new radiator as one normally would. I haven't been able to find any information on this, any leads would be appreciated

Pics here cause idk how to properly post them here so that its visible:
https://imgur.com/a/Ut3XyyA