Yep, virtually every plant needs to change out the leaves when submerged. Leaves that functioned perfectly in open air are very inefficient underwater, so flooding a tank traumatizes every plant for reasons described in the thread
viewtopic.php?f=3&t=16038
However, when you experience massive die off of leaves after flooding, then that normally is a strong indicator that your flow/distribution and CO2 are fundamentally weak and that probably your lighting is too high at that stage of the tanks development. I grow both HC and Staurogyne and I don't have these problems after flooding. The HC will usually just sit there doing nothing for a few weeks and then will become active. I don't use nearly the amount of light intensity at this point as I will much, much later on. People just can't wait to throw photon bombs at their plants before they are ready, and when the leaves start to fall off they blame it on lack of light, causing further mayhem.
The real reason DSM is employed is that the amount of time that the sediment is moist encourages bacterial action and maturation of the sediment. That way, when the tank is flooded then it is practically cycled. People fret all the time about whether the tank is cycled, not understanding that the bacterial population of their sediment is as equally important as the bacterial population of the filter media. DSM mineralizes the ammonia in the sediment and grows huge nitrifying bacterial populations without the penalty of algal blooms. This is especially important for those who use sediments rich in organic content and for those who use Aquasoil Amazonia and the Oliver Knott equivalent as these sediments are high in ammonia. If you flood the tank immediately these soils will leach ammonia into the water column, but DSM prevents this from happening by developing the bacterial populations in the sediment which then convert the ammonia. When you flood a DSM tank that uses Amazonia you will not have this problem of leaching ammonia. Many of the algae problems that we incur at tank startup is a result of unstable ammonia production in the sediment and DSM solves this.
The secondary benefit of DSM is that it gives you time for the plants to grow roots into the sediment. How many times have you painstakingly planted your tank only to see your plants floating around after you flood? Isn't that annoying? Well, plants living in DSM grow roots which gives them mechanical stability in the tank. They also are able to increase their mass more easily because they have access to atmospheric CO2, so you don't have to
buy as many, because you essentially are propagating the plants insitu.
Having said all that, if you then flood the tank and make the same mistakes in terms of lighting, CO2 and flow/distribution then you will have problems caused by excessive lighting, and poor CO2/flow/distribution. You still have to follow the correct procedures.
Hope this clarifies.
Cheers,