Your different methods are causing you to notice the smell more than normal.
I'm making a few assumptions, but if you create an airtight PVC pipe, where did you expect the glue to off-gas? It's going to fill the inside of the pipe, especially if left for weeks. The air volume of the inside of the pipe is pretty small, so it's a high concentration. You probably shouldn't be breathing in the test pressure exhaust when you vent it.
Next you said you "flush" it for several days, but filling a pipe with water and letting it sit, then draining it, and doing that twice isn't a flush. Again I'm making assumptions, but that's what it sounds like you did. Run fill pressure water through the pipe for several minutes with it going to drain to actually flush it.
The volume of water sitting in a pipe is miniscule compared to running water.
I don't disagree, PVC glue and primers aren't good for you. We all just "waste" more water than you to rinse the pipe more, so we probably don't notice it.