This question has come up a few times now from customers and partners – so thought it was worth a posting. You may have noticed that when acting as a delegate that even though you are presented with the limited options of the person you are acting as a delegate for, as you would expect – you are seeing more projects than the user for whom you are acting as a delegate. This is a relatively new behavior – but has been this way for a number of months now. This will only occur if the user you are logged in as is a global administrator in your Office 365 system – or a Site Collection Administrator (SCA) for the site collection you are working in. The reason for the change is that in Project Online customers were accidentally locking themselves out of PWA by removing all their PWA administrators – and then the only way to make a user an admin again was to open a support call. This was obviously frustrating for our customers so a change was made that ensured that a global admin or SCA could always get into PWA and add back the PWA administrators – avoiding the need to call us! You will also see this behavior in Project Server 2016. It also helps with the switch between permission modes in Project Server as you no longer need to specify an admin to be added. Obviously the delegation option is only available in Project Permission mode.
There is no security elevation here – as the global admin or SCA would be able to see all the projects anyway – or even reset the users password and log in as them if they really wanted to – so nothing bad is happening. If you liked the ability to see exactly what the user sees then a good option is to create a new account that is a PWA admin but not a global admin or SCA – then use this account for any delegation work where seeing the exact things the users sees is important.