Look, despite what you think, the aim of the site isn't to mislead you in any way.
In fact, it took me about half an hour to realise this site isn't just a Themes only site.
This is a development site for TinyPortal, a package for the forum software SMF. It does mention this on the home page:
Welcome to tinyportal.co.uk!
This is the development site for the mod TinyPortal, a content managing extension to forum software SMF. You will also find a great number of themes for SMF/TP here, as well as support boards for them.
The main developer, Bloc, who is also a developer for the forum software itself, SMF, also has a passion for graphic design, art and takes pride in sharing that here too by way of his themes.
Now, while I don't wish to speak for Bloc, I'm pretty certain that the only reason that a notice was omitted from the home page, stating that you need to be registered and logged in to download TinyPortal files.. is simply because this is a development site and the home page has changed more times than I care to remember.
I know for a fact that there have been notices stating that you do need to be a registered member to essentially Beta test TinyPortal.. which is what 99% of software development sites require in order to beta test their software. Once software has gone final, public.. then registration is often not required. SMF for example is now public.
If you'd like to suggest adding a small notice to the Home Page and/or Downloads Page, in the feedback board, that would be more helpful than stamping your feet.