BG 15.15 is pretty much identical to Mandukya Upanishad Mantra 6. Just compare the iskcon commentary of that BG verse with the commentary of any acharya of your choice(Sankara, ramanuja, madhva) for the Upanishad verse and you'll notice the difference.

For the BG 15.15 verse, the iskcon commentary states: "He is worshipable not only as the impersonal Brahman, the Supreme Personality of Godhead and the localized Paramātmā, but as the form of the incarnation of the Vedas as well." This is wrong on two grounds. Firstly the impersonal Brahman cannot be made to an object of worship, be ause it has no attributes or forms to be attributed to. You cannot worship something when there is no objective reality to be attributed towards it. Only Ishvara, like Lord Krishna, can be worshipped. Secondly it is equating Ishvara with Brahman. Brahman is the illuming consciousness through which the universe, including Krishna, can be known. 'Known' here not in the sense like how the Vedas or other objects can be known, but in the sense of discovering the nature of the non-difference between anything and everything in the universe.