Yeah, if they're talking to you about you, then they're giving you a warning that you have attendance issues and if you want to avoid a CA you might want to do better about attendance. Not unethical at all, really. They're doing their job as far as keeping TMs in the store and working--giving you the head's up gives you a chance to correct stuff before something official shows up in your file, which is good for you and reduces aggro for your leaders.
Or they're hoping you'll quit because the absences are excessive and they'd rather have someone in the slot that doesn't have attendance issues. If you have a legitimate reason to miss work so much (eg a medical condition, school or family obligations, etc.) then you need to be talking to your leaders about that.