Yes, you don't seem to get four-sided machine-made coins with sharp corners. That being the case, I'd imagine the shape that makes the best use of the metal is the hexagon, yet we don't see many hexagonal coins. It is true, though, that scrap from the blank production process can easily be reincorporated into the next batch of metal in a way that (e.g.) teabag paper can't AFAIK.
If metal wastage was a major problem, we'd probably see fewer round coins. That being the case, I don't suppose it's a major deal. And I'd imagine that the cost of actually cutting the metal with a machine is the same once you've designed the cutting mechanism. If you have a cutter that emits 12-sided planchets, it will continue to do so until you tell it to stop in the same way as one that emits circular planchets will.
Bimetallic coins may be more expensive to produce, but they are nevertheless attested fairly early -- in the British context, more or less concurrently with polygonal machine-struck coins. The halfpennies with a tin plug in the 1680s/1690s spring to mind, plus various Victorian and early 20th-century tokens and Spielgeld.
BTW I think you might be right that the heart-shaped and square tokens on that book cover are hand-cut. I kind of presumed that they'd be machine made if the merchant wanted hundreds of them (which presumably he did, as they're not vanishingly rare, unlike the siege coinage), but then again, back then labour was cheap and machines expensive/non-existent.