PHP extension might be telling. Consider that phpBB had an extention system that didn't have any kind of hooks. All extensions were installed by modifying the code in place. They did not use any of the diff formats already out there; in a gross case of Not Invented Here, they made their own. Took them a while to make their own patch tool to automatically apply their custom diff, and it was buggy as hell.

So that shop might have just been following the lead of one of the most successful PHP apps.

Someone will be along to say "PHP is good now, actually", but I don't care. The community was shit back then, and I don't see why anyone should care beyond legacy software at this point.