Keep in mind i'm an amateur cue builder with somewhat more than a dozen FS blanks in a half dozen/8 years.
About half 4 point, the others 6 point. No veneers yet.
I have aimed for less than 3/32" as turned on 4 point. (& usually do better, but that is where i am not satisfied/will start dicking around moving center at one or other of the other ends)
The 6's are difficult - a smidgeon of sanding on a long slender 6 point will move a point "quite a bit" so have learned to accept about 1/8" as turned. But the fact of how easy it is to accidently move a point, means they can be sanded quite close without changing roundness, and certainly no effect on taper.
Then you get down to what Chris mentions: even with a pencil line drawn while turning the cue by hand on the lathe, it is really, really difficult to decide, in some cases, whether the point is short or long when looking for 1mm. You might think you can call it, but if epoxy was used for glue up, that final line is a bit "adjustable" even when the point appears quite sharp. If there is one sharp point in the bunch and the direct opposite side is short, you know you are off even at 1mm. If there is only one point that appears a "little off" it might not be the points, it might well be the sanding up to that (ahem) point.
To put it in perspective, you are looking at a wood point, that may only change .001" thickness in 1/16" length at that point. (OKAY, sometime when i'm bored, will actually calculate it. Above is a SWAG). But bear with me: every 1/2 thousandth inch you sand in thickness moves any given point at least 1/32" length.
To answer the question from the customer's (ahem, again) point of view, if you make good splices and realize that when turning between centers, *BOTH* ends of the blank need to be dialed in, it is easy to hit 1/8" while turning, that can be refined to much closer, and sanding can put it to within 1mm, where Chris's law of cue observation kicks in.
Of course professionals doing this over a lifetime probably do better. But at some point you are limited by materials, in any substance or field of endeavor. It's going to be easier to get true sharp uniform points with fine grained wood like ebony, and glue will mask more; than perhaps with really coarse grained wood like Wenge. Though any dark wood still gets an assist from epoxy glue.
smt