Farming is generally safer 100% sure exp and gold. Ganks are inherently dangerous and near unnecessary. A laner should be playing just as safe and winning their lane in theory (Only taking sure kills, and focusing on cs). The jungle position originally started as a roaming support / extra resource gatherer. Basically warding and clearing camps. Devourer junglers go back to this root. They sit in jungle farming / warding (River, deep wards, etc) until they hit sated (Can be as soon as 12 or 15 minutes ). Then proceed to take objectives and abuse the sated power spike in the teamfight phase.
Taking potentially unsuccessful ganks at best wastes time (delaying the sated power spike) and at worst gives the enemy team advantages (Extra gold, vision on where you are so they can take objectives, etc). If a team is taking the safest route to win then literally the jungler won't gank unless it's a blatant free kill or planned and coordinated team gank.
I mean one full clear route after hitting devourer gives 20 stacks (5 for dragon, 5 for rift herald, 2x 2 for skuttles, 1x 6 for mob camps stacks). So on a optimal clear pattern you're literally hitting sated on the second respawn of the jungle camps (With skuttles). So it's not nearly as hard as people make it out to be. I mean you can do things in a relatively safe manner to get vision on the enemy jungler and steal his camps for extra stacks.
It also doesn't help that most devourer champions are good at dueling and split pushing. So when team fight phase hits the devourer jungler's group can just pressure but not get caught out or engage while the jungler split pushes and forces 2 or more enemies to react. Then it's just a basic 3 v 4 teamfight while the jungler distracts the 2 that pulled off. If they don't pull off then it's just a tower + kill for the jungler or inhib later on. (Unsafe without pressure on a lane, or deep wards to track enemy movement)
Even with this tactic it's still a good idea for the jungler to fill mid or top when they back. It gives a extra cs + exp advantage over the other jungler. Assuming they don't lose out too much on stacking.