"Conforming implementations are not required to use ref counting" -- statement correct?

[sidkshatriya]

In:

https://github.com/php/php-langspec/blob/master/spec/04-basic-concepts.md#reclamation-and-automatic-memory-management

Despite the use of the term refcount, conforming implementations are not required to use a reference counting-based implementation for automatic memory management.

Is this statement correct? If I understand correctly many PHP projects depend on the deterministic firing of __destruct() function to cleanup SQL transactions or connections.

HHVM elaborates on this:

Eliminating destructors. Deterministic object destruction is the reason why nonscalar PHP values require precise reference counting. This requirement has long been, and continues to be, a sizable performance bottleneck in our optimized JIT-compiled code. Using garbage collection instead could unlock measurable performance improvements, and the behavior of destructors could be closely imitated by a combination of try/finally and other new language constructs.

(from http://hhvm.com/blog/2017/09/18/the-future-of-hhvm.html )