Why is this considered perfect at Nakatra?

https://i.imgur.com/1QLKXlf.png

I had a look at the Perfect Sanctum achievement and thought it sounded like a fun challenge to do the whole thing flawlessly. Until I got to the end and saw this last requirement: Beat Nakatra without being sent to the Shadowsands more than once.

And I don't really understand why this is considered part of Perfect Sanctum. There's nothing you can do to prevent getting sent to the shadowsands except kill the boss. It's not a mechanical achievement, it's a speed achievement. An unfitting speed achievement.

Perfect Sanctum has all these achievements that make you dodge each mechanic perfectly, and then you get to the end where out of nowhere it's just "Kill the boss really quickly". Because for some reason, out of all the mechanics, this is the only one you're not allowed to see twice. You can let the dogs howl over and over again, she can even reach her corruption cap, but two shadowsands and it's a failed run. Why? Shadowsands doesn't even change until you're pulled into it for the 4th time.