I have just got my hands on a Zotac 3080 non oc and it fits perfectly with the front io removed.I don't think it's a different cooler. It's way to expensive to produce different coolers for practically the same card. Mass producing the same will get the cost down. I sent them an email about this, and I'll get back to this when I get a reply
Edit: maybe the 3080 has the cooler placed in a slightly different way, so that the cooler on top is in a different place. Because the components used on the board are different/higher or something
I have tried with the front IO on and found out that the end of the IO cable is touching the third fan other than that there is no problem for me to fit it in. Btw my case is v6.1 but it should be the same as v6.