[schoen]

Maybe a difference of aspiration?

https://en.wikipedia.org/wiki/Aspirated_consonant

Aspiration is contrastive in some Indian languages but not in English. (It's regular in most native speakers' English, but never distinguishes words by its presence or absence.) I could imagine that some Indian language speakers would learn to pronounce English /p/, /t/ consistently as [p], [t] and others consistently as [pʰ], [tʰ], even though English native speakers would have this difference in realization conditioned by other things.

The [pʰ], [tʰ] versions would probably sound "louder" or "stronger" when they occur in unusual contexts in English (I guess, I don't have enough control over aspiration in my speech to record a useful sample; maybe I could synthesize it?).