At the moment view-only guests on dashboards can change the time range on widgets. In our company, we started using dashboards for time reporting to our customers and we need them to see exactly the time range we choose. If they can change it themself they will be able to see all time entries in real-time and to be honest, my colleagues are not strict about adding time entries in real-time and they mostly add them with some delay and it might confuse our customers.