Depends on the tech, but essentially you need to adjust stride length, foot pronation/supination, knee extension and a bunch of things about hip alignment.
Someone walking while looking at their phone will ID differently than the same person walking fast while trying not to run.
BUT, in the same context with the same footwear, these systems are pretty accurate. So in places with CCTV, they can be pretty quick at tagging and filtering regular repeated activity. That way, it’s the unrecognized gaits that get flagged up for investigation.