Sampling the block Spruce Wood Plank results in "Spruce Wood Slabs" with an icon of Spruce Wood Planks and places Oak Wood Planks.
See screenshot for Text Error and Icon.
Note: Only tested with this with Spruce Wood Planks. I'll update further tainted block samples as I go down the list.
[MC-4500] Sample Block Tainted
Sure it's supposed to work this way: If you pick a double slab, you'll get a double slab.
Placing double oak slabs instead of double spruce slabs is another (still open) issue: MC-1959
Is it supposed to behave this way? (Samplings the Double Slabs). What about the issue that placing Sampled Double Slaps results in placing Oak Slabs.
Note: It's quite weird. I have serious OCD about Planks vs Double Slabs, and the wall I sampled from would contain 1 block of Double Slabs. 
No, you're picking a Double Spruce Wood Slab (ID 125:1) , which is a lookalike of Spruce Wood Planks (ID 5:1). The regular Spruce Wood Slab has the ID 125:1.
Destroy in survival mode the questioned block and you'll get two Spruce Wood Slabs instead of one Spruce Wood Planks.
Ah. Thank you good sir...