How can you tell if a job posting is still open?
Check whether the posting is still listed on the employer's own careers page, not on the job board you found it on. Boards keep listings up after the employer has taken them down, so the employer's applicant tracking system is the only source that goes quiet when the role closes. JobShifu re-sweeps those systems and records a first-seen and a last-seen date for every posting.
A "not seen since" date is an observation, not a verdict on the employer. It means the crawl could not find the posting on the employer's page after that date. Roles are filled, paused, moved to another requisition and reposted for ordinary reasons. The checker states what it saw and leaves the inference to you.