Any idea why the non Philips SOX - Es had dimples?

yes i think its because the proper osram e lamps also had dimples, so that continued with the philips made osrams (check the 131w i gave you it has dimples i think)

The E lamps operate at much lower current and therefore take longer to run up. Without dimples it would take an excessively long time for the sodium to diffuse from the bend towards the electrodes. On magnetic gear that is tolerable, but on electronic gear Philips programmed its ballasts to shut down lamps that did not run up fast enough. That created a bad reputation for competitor lamps, which had to eventually find ways to make their lamps run up faster. Double dimples near the electrodes were the solution from Osram.