I doubt someone would take the time to rotate the plant at equal intervals to develop this effect. I suspect one aspect of the water quality is out of wack or that this plant is exhibiting some weird gene expression. That plant is a prime candidate for tissue culture!
If it does continue to grow that way, you have got yourself a mutation!! Hold out for lots of money! All the commercial plant growers are on the lookout for mutations and they charge big bucks for them when they are first introduced. See if you can get up a bidding war between Oriental Aquarium and Florida Aquatic Nurseries! Also gimme 10% of the take 'cause I suggested it
I got a stem off a plant club swap table of P. stellata (same as the E.) that was in sorry, sorry shape. No leaves to really speak of but a good, sturdy stem and decent roots. I planted it up and for about 2 weeks it sort of sulked. Then it began to take off. It firstly produced almost exactly this kind of twisting stem, leaves attaching the same spiral way, all of which I thought was kind of cool looking. It then started to grow normally and in the last month or so I've divided off various branches, sold some, re-grew a few and it's "back" to normal, no more twisting and the stem is now almost the circumference of my pinky finger! So at least in my case it was likely due to severe stress and grew this way until it recovered.
It also looks rather like a form of fasciation that occurs often on flower stems of terrestrial plants (my foxgloves, Digitalis purpurea, seem very prone towards producing them). As this can be caused by damage rather than a mutation I'm not sure that it would be stable when cultured.