'Down Time' in and of itself, is a restriction for an entire device in iOS, hence "Down" time (allowing exceptions, e.g., the Phone app). Simply, if you add certain websites to the SCREEN Time's "NEVER allow" lists, Chrome WILL allow them (whether using iOS or MacOS). Screen Time's "apply across devices" implies the sum usage will be limited on both iOS and MacOS... But, it isn't, especially with Chrome.