He doesn't need them. He'll stop the wood if it flies. BTDT here in the states when someone got me into woodworking and never mentioned kickbacks.Safety devices removed for purposes of demonstration, no doubt
Appallingly dangerous without guards and push sticks.
You would need two pivots to adjust both length and angle. Perfectly possible to make an adjustable jig but far easier to make 2 or 3 different jigs to suit a few standardised sizes of wedge.+1 to bandsaw, tried it yesterday.
Niggle. I now want n holders for variety? Those chunky big wedges for in the garden. Slivers for woodworking.
Never seen a variable angle one... though surely length would need to change to match?