Nozzle height, can you clarify something

Hi folks. I've been having an issue with my 2nd layer not sticking to my first. I contacted the manufacturer (I don't want to name him in case there's just a simple misunderstanding, I don't want to bash him) and he blew my mind. He asked about nozzle height. I told him I use a feeler gauge. 0.104mm and set it to light drag. He said, at the home position the nozzle should be touching the glass because the nozzle will lift 0.Xmm to print my first layer. If I start with the nozzle 0.1mm above the glass, I'm actually adding 0.2mm to the mix. Is this true? Should my nozzle be touching the glass in the home position?
If so, how do you check your bed level? Up to this point, I've been putting the nozzle in the home position, then manually moving the head around the bed and using my feeler gauge to set level. If the nozzle is touching the glass, how do I know if the nozzle is just toughing, or applying force on the glass?
The printer is a reprap design.

It depends on the individual machine. So knowing what you're using would actually help. My printer calibrates from 3 brackets on the corners of the bed, not the glass itself. Some use a built in sensor, some require a dial indicator.

If the guy who built is telling you how to run it, I'd probably listen to him.