Been asked before,
here for example.
Mike wrote:A job activity stage simply starts a job, which will typically take a second or two.
So in your example, a job activity will start job 2, then once job 2 has started, a job activity will start job 3.
Now it's been awhile but that's not how I remember it, nor what I thought the OP reported (assuming they are using Job Activity stages and what 'trigger in sequence' means). They start
and wait for the associated job to complete before moving on, thus Job2 completing before Job3 starts. As Ray noted in the linked post, you would need to use a different stage (Execute Command, Routine Activity) to get a job started in the background for the Sequence to move on and be able to start other processes without waiting.
I've got no way to test any of this and happy to be proven wrong. Obviously, with answers that are polar opposites, one of us must be.