Is that a bug, or that's how it's supposed to be? Destryoing Pillbox rewards in spain mission

Hello, I hope you are doing well. as the tittle says I don’t know the issue but. Destroying pillbox in air RB (with premium account) in Spain mission is equivalent to destroying the artillery or howitzer ground targets. even though the pillboxes takes much damage to destroy it.
Pillbox in spain gives you about 300 SL and 10 RP when destroyed.

PILLBOX reward:

Howitzer reward:

HOWEVER! in almost every maps like
•Golan heights. they are much different.
as pillbox in these maps gives you 1.3k SL and 100 RP.

So I don’t understand what’s the point or how it’s done.