Bug or not: accel_init_interned_string_for_php returns non-interned strings

I'm investigating the various segfault bugs in PHP 7.3.0. I was looking at ext/opcache/ZendAccelerator.c:545 and :552, where accel_init_interned_string_for_php returns normal strings instead of interned strings. As I understand it, there could be (buggy) code which frees a string prematurely (possible with normal string but would not happen with interned), causing corruption. Is this a bug or just some Zend quirk?