Yeah. That's a reload with retention. That is legal.
The speed reload is to dump the mag with a round in the chamber (not at slide lock). That's too gamer and therefore illegal.
Because in real world, you'd want to go to a new position with empty mag but one in the chamber, start to engage multiple targets, but after one round you gotta reload. So, now the multiple bad guys have been made aware that you're there and since you only fired one round and now are empty, you gotta reload while they're returning fire.
This is not a sound tactic but IDPA can't allow the speed reload because it'd be too USPSA so they basically go against their own "Fundamental Principles".
At least that's how I see it.
In a real life situation I'd want to be dumping/replacing the magazine, while still having a round in the chamber, when moving behind "cover".
Oh well. The rules are the rules.