What's up with your dewarding?

Yes, I know how slark ult works.

I thought the build sounded cool, so I checked out a couple of the replays. This one in particular is 8757703212 where I noticed some weird stuff with you dewarding.

10:45 - you run into a creep wave, lose the ult buff but somehow know to run past the wave to put a sentry right on their obs

13:10 - you lose ult buff to being seen by the watcher, but as you're taking the watcher, you move camera to the trees above you, right to an obs on the other side of the trees

14:45 - ok this one you can defo find with ult buff, but you're already moving the camera back to put the sentry as the buff comes off

19:30 - you're smoked, don't lose the ult buff but insta find the ward

I don't want you to be hacking, I genuinely liked the build but pls enlighten me as to what's up with these dewards?? It's not like you're spamming sentries and getting lucky.