Cut a dado groove with a 3/4” diameter router bit and you’ll almost certainly have a too-loose joint when you try to plug some 3/4” plywood in place. Under the guise of metrification, sheet material thicknesses have all shrank enough to cause problems with joinery if you rely on the old, Imperial thickness designations. And besides, material thickness varies enough from sheet to sheet that it can make a difference when it comes to prominent joinery. This is even true in the USA that still uses Imperial more or less exclusively. Sheet goods remain thinner than their name specifies.