Ullillilia, with all due respect, this is nonsense. The dynamic flag is not set at all on static entities. You're just setting it by assigning your action, and then resetting it again. Thus the only effect of following your advice would be a slower level loading.
Use some common sense: If you really would get a 25% better frame rate by assigning an action that just resets a flag, don't you think that the engine would then have that flag not set anyway?

. In some cases it can even help to _set_ this flag (by assigning an action) if you want to prevent the automatic animation of a model, which consumes rendering time on very big models.