I bought one of those telescopic lances a few years back thinking great that would clean badly stained plastic gutters & facias. Nope it didn't and I found out if I was not careful would see bits of fascia trim flying off etc also gutter joints starting to leak.
Regarding jetting out domestic gutters to clear them that's bonkers if they are full as crap just goes everywhere. Not only that can force water into the roof space too.
I often come accross in gutters broken bits of tiles, roofing motar and many other odd things which can get stuck in the downspout bends using that method.
Not only that I have found not many ppl want a pressure washers used on their house.
Each to their own I suppose