3mm is slightly larger than a roofing nail (about 2.6mm) so it is not very big.i reckon, if MC tires got ridiculous expensive, maybe, but still have my doubts. 3mm is pretty big?
Generally if the puncture is greater than 3mm I rather use patch/plug. As you say the slim plugs cause no additional damage like reaming and work well.That’s a good idea. I didn’t know they made a slimmer plug. It always feels wrong reaming out the hole to further damage the tire just to get the plug to fit.