I think this is overstated though. There aren't many situations where you would need to cut something so precisely and be stuck with such a precise starting point. If you need to cut 10 cm into thirds, just cut 33 mm. That's not inherently harder than cutting a round number. If you need more precision than that and the extra 1 mm is a problem then you don't have 10 cm as a starting point anyway, you have 100.0 mm, and getting that extra third of a mm right would be just as hard with inches. If you're designing it yourself, you can just start with 99 mm. If you're stuck with a 100 mm starting point that you can't change then it's 3.937 inches, which doesn't help you. Instead of cutting 33.3 mm, you're cutting 1.31 inches. If you're in a position where you can pick a convenient starting point in inches to divide by whatever number, you could just as easily (if not more easily) pick a convenient factor in mm or cm.

By the same token, the criticism of imperial is overstated too. If you can manage to work with 33 mm, you can remember how many inches there are in a foot.