As I have stated before, he would not have been remanded if it was not serious. He obviously was not remanded to do with cyber crimes, as he had already been arrested at an earlier date, when they took his computers at that earlier date, they have found his stash of kiddie porn and rearrested and remanded him.
Again, I cannot speak to the UK excepting that the country is often a proxy for US, so I will look at this from a US criminal justice perspective.
Often when a person is arrested their electronic equipment is seized and forensically examined. If anything, no matter how minor, is found. then new criminal charges are filed (stacked). This is based on the theory that the more criminal charges there are, the more likely there will be a conviction on one of them. I am aware that one of the differences in criminal justice is that on paper (reality is different) in the US a person is innocent until proven guilt, while in the UK a person is guilty unless proven innocent. The other major difference that I am aware of is that in the US a person has the right to silence, while in the UK a person does not.
Going to the hacking/ddos charges, we have to look at what they may have really been. As an example, a basic attempt at ddosing is a ping attack While ineffective for a single computer, ping -t some IP or website, will launcha continual pinging in Windows. There is a legitimate need for a continual ping in some instances. Unless you have a very large number of computers or a large botnet pinging I would not call it a ddos attack. Again as an example, I have been using a continual ping to attempt to load a new OS/firmware into a bricked router via tftp. Then again, anyone can boot Loric. Launching Loric against a government site would not be wise, but people do it just to learn how the program works. Is this hacking or exploration. Often people engage in port scanning. There are legitimate reasons to scan ports, but executed improperly it will look like a ddos. Perhaps the guy fired up Acunitex. Acunitex is a vulnerability scanner that does have the ability to launch a ddos, but its use is often innocent. These are the things that are missing from the information set that we have - what was done and how.
Governments around the world are skitzy about perceived computer attacks. partially this stems from the NSA invading computers of other government agencies and partially this comes from legitimate attacks from China, Russian, Ukraine, and some of the Mid-East countries. The problem is that very few of those agencies would recognize an attack, so they jump on anything. For this reason alone, I am sceptical of any claim of hacking.
I know 13 y/o's that look 19, and 19 y/o's that look 13. Calling an age on appearance is flake at best. Appearence is all you have on a computer unless you fill in details. However, in the UK you would have to explain the appearance. In the US it is even worse because people have been convicted of child porn for cartoons.
The only thing that I am going to is that we, as outsiders, really have no information that the government has not shared with us. I have little trust in government.