Great breakdown Big Dave. This is all dealing with what is called volumetric efficiency. The goal of choosing a cam for a N/A engine involves a number of factors, but the main goal is to fill the cylinder with as much mixture as possible for the given use of the vehicle. For the street you need some low end torque and a good power band throughout your RPM range, so you want to shy away from big overlap cams with tight LCA's. ("lobe center angles").
The issue of some of the intake charge backing up past BDC is called 'intake reversion'. The charge doesn't actually go past the carburetor though, it simply mixes back into the plenum and goes to other cylinders on the intake stroke. This reversion is very minimal but when running cams like this it will play games with power brake boosters due to lower idle vacuum. When you get into tight lobe center angles on a race cam you can run into exhaust reversion that can be problematic, causing intake charge contamination. Most average street guys don't have to worry about this.
Another thing that affects advertised compression ratios of a piston is the size of the chambers in your heads.