They're "overthinking" it!
Why did they feel that they had to figure it all out first instead of just following the installation instructions? The issue is probably because they've never seen anything like our little power sensing gizmo before so they trying to figure out how on earth it can possibly work rather than just accepting that it does
and get on with the job. We designed it so that a complete novice with zero experience of car electrics can safely fit and power 12V accessories under the hood in seconds. Sometimes installers tend to overcomplicate it because they initially assume that it just can't be that simple.
In my experience, installers tend to fall into two camps. The "I've always done things this way" group and they tend to struggle with the first job because it is too simple and it goes against what they've always done before. Then there's a second group who realise that it can save them up to an hour on the job so they can get more done in a day.
Consumers just do it and it works. In fact the only real problem a consumer encounters is that they forget they have to start the car's engine for the jammer assembly to switch on.
On a side note:
If someone does want to go to the trouble of fitting the Blinder traditionally and having the Blinder kit inside the car, they are obviously free to do that. If you still want the Blinder alerts to come through the mirror, you can just hardwire our interface inside the car too, in the traditional way, so that it passes power through to the Blinder control box and takes the Audio out from it. If you're doing an instal from scratch it takes longer but say someone already had a Blinder fitted and then bought the GPSmirror and wanted them both to work together, that's what they'd do. In those circumstances you don't have to move an existing blinder instal to the engine bay - you just hook it all up inside the car.
I guess some people just like making it hard for themselves.