The farther you get from the source the lower the pressure will be. A home only really needs like 40psi to operate correctly and many times has 100+psi that needs to be reduced because of this.

Also a small leak is not going to noticeably drop water pressure in a 6" main

That's really not that much water if you've ever worked around utilities. It's about the equivalent of a half inch copper line.

From a quick googling a residential sprinkler system uses between 12-30 gallons per minute. So about half of what it takes to run a sprinkler system

I do love stupid articles like this. They make it seem like it's something innovative yet it's been around for a long time already. And I especially agree with it needing to be tethered to get pulled. The wifi one get stuck in a pipe, you just leaving your $25000 camera down there? No, now you need to send people in just to recover it before it causes a back up

Plumbers putty will dry up and crack away of used to fill that gap, won't provide a water tight surface, and would take a lot to fill that. Backer rod would be the appropriate backing for silicone, not caulk