Yes the USPS tracking information is delayed and not updated in real time.
So if your package gets scanned then the USPS tracking may not update for an hour so even after it's been scanned.
USPS tracking is not the most reliable tracking and sometimes it may not update for a few days.
Then later it will update once the package is scanned again.
So it's not worth the time to check USPS tracking more than once per day because it does not update that often.
Also when your package is on a truck or plane it will not be scanned and if it's on a truck the package may not get a scan for a few days while the package is traveling to you.
So checking the USPS tracking information more than once per day is just a waste of time because it will not update that often.