Passing Etiquette

Hi all!

I got told recently that a habit I have might be rude, and I'm fully prepared to get downvoted into oblivion.

Talking sucks when you're trying to breathe, and sometimes I'm nonverbal anyways. [Edit for clarity: sometimes I literally cannot speak, irrespective of whether I'm exerting myself.] So when I need to pass a group on a trail and they're blocking it needlessly, (e.g. I could pass if they were single-file and there are no hazards) I'll pace them about 5-10ft back for 50 or so feet, long enough for them to hear me tramping around behind them if they're going to, and if they don't notice me I'll scuff my shoe on the ground to make a loud but not terribly obtrusive noise. This gets the attention of the last person and they'll usually call to those ahead of them and scootch so I can get through. I've only had this fail once or twice.

Is it rude to do that? [Edit: If so, what do you recommend I do instead?]