in general groups should stick together when hiking, but there are times when it's ok to split up too. i usually hike solo, but on the few occasions i've hiked in groups, it's not unusual to split up into a "faster" group and a "slower" group. if you have enough people so that each group can take care of itself, this is perfectly ok. everyone has their own ideal pace: it can be very frustrating to be forced to hike at a slower-than-normal-for-you pace, and can be almost as mentally and physically tiring as being forced to hike faster than normal. you just need to avoid the situation where someone splits off from the group and is alone by themselves, that's when people become lost or have emergencies.
also, hiking in groups can foster a sense of dependency on the group that can make getting separated more dangerous than if you expect to be alone from the beginning. even if someone is hiking as a group, i believe it's the responsibility of each hiker to be fully capable of doing the hike by themselves if necessary, meaning each person should know the route as well as if they were planning to go alone, should have all the knowledge and gear to do the hike solo, etc. even if they start as a group, there are potential circumstances that could require them to split up. what if there's an accident or injury and there's only one person capable of hiking out to get help? that person needs to be able to do that if the situation calls for it.
even if i go on a trip with a big group and multiple guides, i still make sure to have all my emergency gear, a map, a GPS route downloaded to my phone, etc. i always imagine the worst-case scenario and make sure i'm prepared for it, however unlikely.
