Hi mrsnak,
of course you are right: an intended breach of symmetry can even be more appealing. I just thought about asymmetry in haircuts or clothes (or try to imagine any art which strictly obeys to geometry).
And I also take your point that a crown at the 9 o´clock position would have overemphasized the importance of the helium valve crown.
Saying this I think, IF there has to be an additional crown it´s well done, but the initial poster questioned the overall need for ANY.
We often have complications in our watches that we do never practically use, but we nevertheless value them, be it for their technical achievement, historic tradition or beauty. For example, there are admittedly only very few people who NEED a moon phase (which includes me). But I like this colourful complication very much. If you have a complication that you do neither need with regards to its technical solution (like the helium escape valve) nor like it for its design/beauty properties, it is a legitimate question to wonder whether the manufacturer does not leave it out.
But as I said before, I do not see Omega doing this and obviously the crown is not a disturbance for everybody. Look at me: I am not fond of the crown, but I like the SM 300 very much for the rest of the watch apart from the second crown
.


Kind regards,
anaesdoc