The US has robust IP and trademark law that allows companies some amount of chance to find a legal remedy to anyone who clones their business. China is notorious for protecting local companies from foreign IP suits.
Further, at a lot of companies, the risk has to be acceptable to shareholders and auditors. Perceived risk is often a more powerful motivator than actual risk.
Some of the software I've written _explicitly_ disables scheduling mobile notifications during the transition periods so I was also very confused by that. Your ET speculation makes sense to me. I'll bet that whatever server/containers being used for the backend were running in the Eastern Timezone.
Further, at a lot of companies, the risk has to be acceptable to shareholders and auditors. Perceived risk is often a more powerful motivator than actual risk.