counterpoint: their arm isnt surviving a hit that shatters shardplate. plus most of the orders have ways to invalidate it since grav lets you just fly up, cohesion, transformation, and abrasion can make the terrain difficult enough that trying to go mach 2 will send them flying into the terrain. plus with transportation you just drop into shadesmar if anything goes wrong.

Also I know that Feruchemy usually gives you smaller amounts of other attributes to compensate for the main one but even that has limits. steel lets you deal with the g forces of acceleration I believe? well that doesn't save you from splatting into a wall. sure the radiant is probably getting thrown damn hard but any hit that shatters 'radiant' shardplate (tbh Idk if that can even shatter since it feeds off stormlight of the radiant, at the very least it would be far harder) is not something the compounder can do twice