Hamilton was purposefully backing into Vettel in Spa, if you look at the lap charts he came out of the pits on a 109 second, he had I think like a 3.5 second gap immediately after Vettel came out of pits and he dropped back to do two laps in the high 110 second range, backed right into Vettel, backed in a little too much and did a 108 to re-establish the 1-1.5second gap and then went on from there. Every time Vettel tried to gain 1-3/10ths, every single time, Hamilton pulled that out next sector to keep him out of DRS. That was win as slowly as you can.
He was cruising here but don't forget that Ferrari aren't stupid, once they passed Ocon then started cruising also. They were ~5 seconds behind Bottas at that point, closer to 10 behind Ham and had no chance to win. He kept it kinda close up to the pitstop but after it, with no pit mistakes and pitting earlier so no undercut Ferrari backed off even more.
If Vettel had been closer, say 3rd on the grid and within a few seconds of Ham, I think we may have seen Ham back into Vettel again, throw him dirty air, see if that hurts the engines come the end of the season that may matter, but the gap was too big, Ferrari gave it up very early and everyone but Ricciardo was saving engines once an order was pretty much established.
I forget which race it was, Ham was a few places behind for some reason, he was gaining on Kimi but at some point not long after the final pit just gave it up and ended ~25 seconds behind or something. When you know you can't win there is no reason to take more out of the engine than you need to. So the gap in Spa was bigger than people think and the gap in Monza smaller than people think.
