I shall explain why Non Ahmadi view of 33:40 is wrong through Grammar.
Firstly some grammar:
-We need to focus on the Arabic word لكن
-It means 'however' or 'but'
-Arabic Grammar teaches us that the word is used for the purpose of 'istidraak' which means correction, rectification, or amendment
-The word appears between two statements opposed in meaning, if the phrase before positively affirms something, then the phrase after would be negative
-If the phrase before is negative then the phrase after would be positive
How does that apply to the ayah?:
-Allah the Almighty states that Prophet Muhammad(saw) is not the father of any of your men, and negates his physical fatherhood
-After this Allah uses 'lakin' and makes another statement.
-The word tells us since the biological fatherhood of Muhammad(saw) has been negated in the preceding statement, the following statement would affirm his fatherhood.
-Classical Sunni Scholars like Imam Razi(rh), Imam Baidawi, and Imam Zamakshari had this view as well.