Let's jump into an example here. Meep making lime from fossil which is a high priority for him. Inside that rock granulator, there is still 200kg fossil available, and compactor right next beside him have more than 15t fossil. Next task in his to-do list is a standard priority at most.
After he makes one lime, we would expect he continue making until no recipe available to do. But he didn't, he will grab that standard job and will back to granulator if that job still available.
This is not happening in QoL3, and I believe not intentional. Probably job lock to prevent other dupes stealing the job from him also lock him to get next job on the same machine.
Steps to Reproduce
Make order 99 lime making on rock granulator. Make sure there is a lower priority task available for that dupe and he will bouncing between jobs.
This issue has been fixed in either a future version or updated in a previous version.