well, some companies strictly follow the policies only, so if the hour stated 8am to 5pm, you come in sharp and leave sharp je, dun rugi to the company.

whether they got grounds or not? likely because you're the one who is in contravention of the policies? it also depends on your boss, whether your boss ok or not.

last time my company 8.30am but clock in 10am or so also no problem for us, why? because we work round the clock, when we work until morning, nobody bats an eye.