Sutra:
240. upakAra Smruthiyum caithanyAththAlE vanthadhu; upAyaththil antharbaviyAdhu.

Sri PBA Swami's Sarartha Deepikai:
But should not the chetana be having gratitude for what he is getting? Then can that not be considered as part of the means?

No, it cannot. As Azhvar says "ennaith thee manam keduththAy" and "maruvith thozhum manamE thanthAy", this feeling of gratitude that he has comes due to his knowledge. This cannot be taken as "the Lord will do His act only if this gratitude is shown" - therefore it cannot be taken as being part of the means.