Yep, I’ve tried 28mm ones on 19mm internal alloy rims. Still took a little work to get on but was considerably better, just normal tight ish tyre. Blew up to bang on 28mm in size.
Conti suggest that 28c to 32c will be fine upto a 25mm internal width rim and its fairly unusual for the manufacturer to say that in my experience but does mean I will probably try 30c on my LB WR45's at some point for better rolling.
Have you used the S TR version? Which tyre/rim width? Cheers.