Philip didn't expect Gerard to join the Organization, but he didn't refuse him, this will give them that big Advantage and also they can secure protect both of the Special and the chosen if Katherine really is the Chosen One, the fact about the prophecy for both Gerard and Katherine remained to be unknown.
Gerard needs to evolve successfully without any external aid of enhancement before they could get a blood sample, same as Katherine she needs to be awakened first before they can test her blood sample too, and also this is if the two is willing to carry out the test, they will respect their decision at least that's what Philip stands.
