Yes, I believe this is normal for all EMs. There are possibly a few exceptions (at least one game awards you 10x for dropping two targets at the same time)...but generally you need to wait for a shot to be fully awarded before you can get credit for the next.
Explaining this just now makes me wonder if that's why it's very uncommon to see awards worth 600,700,800,900...as it means a lot of spinning of the reels where you can't score other points.