I do usually have left over wall material but the thing most of the paver we buy have to be bought in whole skids so I have to get it in amounts of ~125sqft so if the patio is 680sqft I have to buy 750sqft. The block comes in smaller amounts so its easier to get it closer.
plus I dont like using the older pavers on the same job with newer produced pavers incase wear or fading doesnt match. With the block I can use the older block for the course that is buried.
But when those build up or we get slow I use them too lol
( I know you were referring to the RR tie wall but that ties into steps and extend past the photo and I would need A LOT of material to replace that.)