I think the only real reason for the adjustable cheek pad is when using BIG scopes on ramped rails. I've got pards who are running 50mm NF scopes on 20MOA bases and they still don't need adjustable stocks USO scopes prolly do however.
Angry has it right, at least in my case. I ordered the adj piece thinking I'd need it. Instead, it's screwed tightly down. My other A5 and A2 do not have them and they drive nice. Damn fine chunks the A5s are.