launchctl list doesn't show StartInterval
StartInterval won't get printed with (sudo) launchctl list [label].
Use sudo launchctl print system/[service-name] instead. It will be printed as run interval.
Depending on the domain/service target use
user/<uid>/[service-name]login/<asid>/[service-name]gui/<uid>/[service-name]
instead of system/[service-name]
Examples:
host:~ user$ sudo launchctl print system/com.apple.collabd.expire | grep interval
run interval = 600 seconds
host:~ user$ launchctl print gui/501/usr.homebrew.mxcl.autoupdate | grep interval
run interval = 7200 seconds