scoring is a far greater risk (than say with a FD) because there will be substantial torque going through the clamps at times.
Clamps themselves vary; some are flexible enough that the pressure will be applied fairly evenly, others are more rigid, so local pressure is more likely. The latter sort are very much more intolerant of small mismatches in diameter.
Possibly the handlebars are reinforced where the 'recommended' tribars are meant to fit. If your tribars are similarly spaced and the clamps fit/are of similar design, you ought to be OK.
cheers