The expeditious retreat spell (which has a casting time of a bonus action) says:
This spell allows you to move at an incredible pace. When you cast this spell, and then as a bonus action on each of your turns until the spell ends, you can take the Dash action.
However, with a strict reading of the wording, it says "when you cast this spell … you can take the Dash action". It doesn't add "as a bonus action" on the end (like how, say, the rogue's Cunning Action is worded), which implies that the "you can Dash as a bonus action" part only comes into effect on subsequently turns, and dashing this turn still uses an action, since it only specifies the bonus action in the context of the subsequent turns ("then as a bonus action on each of your turns until the spell ends").
If I wanted to cast this spell, then Dash, would I still have my action to use for something else on that same turn? My strict reading seems to imply "no". I'm fairly certain my strict reading is wrong (at least not RAI), but why am I wrong?
There are other questions on this site about this spell, but none of them specifically address this wording that I'm focusing on.