Extradition of mumbai suspects using SAARC convention

An informative article from Daily Times, Pakistan (Next steps after evidence from India) that talks about India invoking "SAARC Regional Convention on Suppression of terrorism (1987)" for extradition of Pakistani suspects in Mumbai attack. Article 3(4) says:
"If a Contracting State which makes extradition conditional on the existence of a treaty receives a request for extradition from another Contracting State with which it has no extradition treaty, the requested State may, at its option, consider this Convention as the basis for extradition in respect of the offences set forth in Article I or agreed to in terms of Article II. Extradition shall be subject to the law of the requested State"

It is important to note that the extradition is optional and not binding on the "Contracting State". It appears that this is just an enabling clause and Pakistan is not obliged in this case. The daily times notes that India has not invoked this treaty in the 1999 hijack of Indian airliner to Kandahar.