Is this representative of a semantic feature of Hindi or is it just the way it's done?

I always assumed (1) that it is an artifact of some phonological features of their first or native language, and (2) it also resulted from their mainly learning English from other non-native speakers and that the lilt was simply a new accent for a regional type of English.

On reconsideration of your question, I take it that you mean some phonological features, such as phonological tone in English can be used for syntactic purposes, e.g., turning a statement into a question by a rising tone on the final word or syllable. Or, affected a quality of voice, as in the sarcastic answer to somebody's question: "Yeah, right."

Also, I have not noticed any great difference in accents amongst speakers in the north, who in the main speak Indo-Aryan languages (such as Hindi, Bengali, Marathi, Gujerati, etc.) and those in the south who speak Dravidian ones. They are really quite different groups of languages, genetically, phonologically, and syntactically.

Ceci n'est pas un seing.