Endurance would certainly be affected less. This affects juniors on the whole and on road there is little specific for juniors other than standalone road relays.
The XC leagues and the XC championship pathway is the one that will be most affected from an endurance standpoint.
Wider in athletics there are huge issues though. Hurdles for example will have one technical spec for schools and another for UKA. In an event like that you cannot coach 2 specs effectively and there will be similar issues for throws.