I don't believe it's a bug.
You can earn towards this mission with every game you play while you work on the class-specific missions. While you play the CV and DD missions you are likely to earn quite a bit of this here.
Keep in mind that you only need 6 missions out of 9 to complete the "5. Battle of the Tonelero Pass" directive. You can skip several of these, including the spotting damage mission if you so choose. The purpose of needing only 6 out of 9 completed is so that you can choose which ones make you go, "Blech! Not for me, thanks" and complete the ones that seem more reasonable to your playstyle.
For me it would probably look like:
#1 - Win 6 Battles (any ship)
#2 - 46 "Hits to citadel" or "Set on Fire" ribbons (any ship)
#3 - Earn 95,000 XP (any ship)
#6 - Get 89 "Set on fire" or "Caused flooding" ribbons (cruisers)
#7 - Get 1050 "Main Battery Hits" ribbons (battleships)
#9 - In one battle, get 4 "destroyed" ribbons (any ship)
Those are the ones that fit my playstyle. I ommited the DD and CV heavy missions, but I suspect that a very strong CV player like @Merc_R_Us or @ReimuBakarei would have no trouble earning that amount spotting damage over a day or two while playing CV's.