I wondered about that too. He said "a little bird told me". I wasn't sure that it was Eugene. How would Eugene know? It then cut to Gregory in the next scene (I think), which I thought implied that he had informed the Saviours, but he hadn't left Hilltop yet so how could it be Gregory? Unless the two timelines were…

"It means he gets results you stupid chief!"

Frasier: "Dear God, it's the end of the world Niles!"
Niles: "I'm afraid it is brother. That was the last of the sherry!!"

Zing!!

To be fair, the doctor seemed like a bit of a tool.

The writer of the article certainly seems convinced that Eugene has gone full Negan. I had just presumed when I watched the episode that even if he was submitting completely to Negan's will for now, he'll change his tact as soon as the opportunity arises and return to Rick and co.

The Doc was obviously an experienced furnace diver. In fact, for any young kids out there wanting to get into furnace diving, they should study the Doc's approach - legs pumping, streamlined body shape, arms out in front, head down - perfect technique.