I have a habit of checking clear apertures whenever I get a new telescope. Going on (a three year old) memory, the clear aperture of my AR152 when it arrived was close enough to 152mm for me to accept 152mm as its clear aperture. If it had been any other value, to the closest millimeter, I think I would have remembered. For example, my 50mm Galileoscope has a clear aperture of 47mm.
The diameter of the OTA, as measured today, came out to about 156.3mm(+/- 0.5mm); but that number is based on the length of a strip of paper wrapped tightly around the tube (at one location only) divided by Pi. So there's room for some additional error. The paper strip had to be longer than the circumference of the OTA in order to fit around the OTA.
The dew shield has a fairly tight fit, so I didn't feel like removing it again. I've removed it on at least three past occasions; probably to measure the clear aperture, to re-seat a rubber seal and clean the residue that the out-of-place seal had left on the objective, and to tweak the collimation.
Best guess: ES's "158mm" number is for the OTA diameter.