Yes, they do contribute to your gamerscore.
According to TrueAchievements, both games can only be played on iOS 8.0 or higher but not 10.0 or higher, Spartan Assault has 5 unobtainable achievements, and both games have been removed from the Store. I believe both games contribute to your Halo gamerscore on Waypoint.
I'd like to think that they'll come back up at some point but I honestly don't think they will.Do the iOS versions support the recorded achievements for Waypoint? Or just the Windows Phone version? I had previously bought the games on my iOS and would download them again to get those achievements.
BTW, if you ever downloaded the iOS versions of the game, you can redownload them from your purchased apps in the app store.Also this.
I took screenshots before and after unlocking some achievements on the iOS version of the game, yes it does still work if you already own the game on iOS 10 and higher but it isn’t recording my achievements here on Waypoint, only on Xbox and only if I click the view achievements itself otherwise it says 0/200.
If any of this makes sense? I can go into further detail if need be.