Basically this, only guy so far that knows how it should work.
In retail you could shadowstep the cannons all you wanted, you could even blow relic doors and click on relic without destroying yellow gate, if you had enough rogues. However, you shouldn't be able to take any bomb from behind yellow gate while it's still standing.
Retail video for reference:
https://www.youtube.com/watch?v=JVmVcVA5E80&t=2m50s
He shadowsteps, goes to where bombs should be (there are no bombs cause yellow gate is still standing, then comes back few seconds later after gate falls - bombs are there).
I didn't play sota for few days and I'm not sure how exactly it works here, but if it's any different from what I just wrote then feel free to use my comment and report it into bugtracker.
TL:DR
No bombs spawned behind yellow gate till it falls down.
Shadowstep / feral charge is blizzlike.