SilverStripe makes use of object oriented concepts so extensively that it flat out doesn't work with PHP4. I don't think your faults with those two files prevent SilverStripe from being a good nor an object oriented framework. Many of them seem completely trival; using <? instead of <?php isn't a flaw. Additionally, main.php might include a bunch of files, but the primary logic is performed via two very quick OO lines of code!

$dir = new Director();
$dir->direct($url);

Finally, core.php is about 50 lines long, and so if it contains functions, its hardly offensive in an application with hundreds of PHP files, most of which contain only classes.

Instead of critiquing those two files, I suggest looking at the tutorials, which demonstrate how you are extending classes that are in the core of the system. It is this sort of activity that you are working with when developing SilverStripe websites, and hence you are very much working with an object oriented coding methodology.

If you have some suggestions on how to improve the system in terms of how developers use it to build their websites, the silverstripe core developers would be intereested in constructive suggestions in the silverstripe.com forum...