If you move a hone up and down "quickly," you may end up with a much greater angle than 30 degrees. This could certainly create poor sealing capabilities.
To judge the angle you produce, take the up-down hatch marks, and estimate the angle between the two. For example, see
A greater-than and less-than symbol >< back to back are about 30 degrees (each) in this type font and represent a good cross-hatch.
The area below the oil ring land is called the skirt. The skirt, over time due to contaminants will wear. I've seen engines with 1700 hrs. with less than 3% skirt wear pattern. All depends on environment and maintenance. 20% is considered to be the max. amount before it's over spec. When the skirt is very worn, the piston cocks in the cylinder. Rings can't seat right then, and often skirt cracking occurs.
This is an example of excessive wear, resulting in a skirt crack:
When measuring skirt clearance with a feeler gauge, a flat blade one will flex enough to check the fit. That is, unless there's so much wear you get up to too thick a blade!
I've never heard of bore being intentionally tapered. Unless you loitered with a hone, don't know how you'd make it tapered. You can't do that with a boring bar - at least none that I've used. Taper is a result of uneven wear, not machining. The top end is usually worn the most, just below the "ridge" if one has formed.
Without seeing the manual the specs. (and thus the context) you cite are derived from, I can't tell you but usually a bore or piston will have an original dimension, often with an allowable deviation. However, 0.001" is a lot of deviation for a machining process, but for an air-cooled lawn mower engine, 0.001" is not a lot. So, the orig. spec. could be 3.125", or anything up to and including 3.126" being allowed. Valve guide clearances are a good example of more "slop" being permissable over say a liquid cooled car engine. Almost double the clearance is allowed by spec.
Ring side clearance. This can definitely affect compression, and to my best recollection about 0.005" would be about max. spec.