Seems pretty obvious to me. If DC beats Stipe and retires afterwards (relinquishing the HW Belt in the process), the vacant title fight will almost assuredly be between Ngannou and someone else. Ngannou is nearly guaranteed, so who would be the man opposite him?
JDS? Nah, Ngannou smashed him. Cain? Nah, Ngannou smashed him. Blaydes? Nah, Ngannou smashed him twice. Stipe? Nah, would've just lost 2 title fights in a row. Beating Ngannou the first time shouldn't be enough to warrant a 3rd. Lewis? Nah, already knocked off by DC and JDS. I can go on.
The only heavyweights that would make sense are Overeem coming off of 3 consecutive wins since his last meeting with Ngannou and Harris coming off of 3 consecutive wins. Harris may only be ranked #11 and Overeem #7, but that's the state of the heavyweight division right now.
Basically I think there is a good 50% chance this is a title eliminator.