Those recruiters most likely have "mastered the language" and are expressing themselves clearly, just in a different accent.

If someone interacts with Indian English speakers often enough that they develop a habit of avoiding Indians just in case they might call and speak with an accent they can't understand, it's probably time to do something about that, like getting more exposure in an environment where it's easier to understand (e.g. with subtitles)

In the case of recruiting, where there's no obligation to pay any attention to recruiters at all, it might not be much of an issue, but it's only a matter of time until you get an Indian colleague and avoiding them is no longer an option.