List started pipelines regardless of start date

The runtime IDs returned can be in different states of activity. You would need to cross-reference them individually using the Pipeline Monitoring API to get that level of detail.

IF you look at the documentation,

https://docs-snaplogic.atlassian.net/wiki/spaces/SD/pages/1438155/Pipeline+Monitoring+API

last_hours - integer - fetch data for last n hours. Max limit is 2160 hours (90 days).
default = 1
pipe_name - string - fetch data for a particular pipeline
org_wide - Boolean - fetch data for whole org including all phases
state - string - fetch data for particular pipeline states.
State: [NoUpdate, Prepared, Started, Queued, Stopped, Stopping, Completed, Failed]. (case sensitive)
    Queued - Pipeline is queued for processing, all pipelines start in this state
    NoUpdate - Intermediate state at startup
    Prepared - Pipeline has been prepared
    Started - Pipeline has started execution
    Completed - Pipeline completed successfully
    Failed - Pipeline failed
    Stopped - Pipeline was stopped, by user or by the system, indicated by the 'stopper' key
    Stopping - Pipeline is stopping
    Example: state=Completed,Failed

In your case, you would want to put a max time for last_hours and fetch your interested statuses

Hope that works out of you.

That is correct, Kim. The active pipeline runtimes returned by the API should all be active pipelines that the Control Plane sees as running regardless of when they the time at which they were started.