Harmless, seems a little too much, in my observations. (For a shrimp only environment)
While they represent some food competition to a certain degree. I concur that they are not going to starve cherry shrimps anytime soon.
They are by far the best substrate and glass maintenance crew you could ever get.
But there seems to be an annoying "factor" where their presence makes the cherries very nervous during molting time and you can see freshly molted shrimps trying to escape "something" in the tank. In addition of strange disappearance and somewhat unexpected deaths.
Since there is nothing there besides, the seed shrimps makes wonder !?!
In a tank with fish it's another story... They have a really interesting cycle of life, that force them to have a swimming period in addition of a resting period. So they become fair game for snails that eat their eggs and then fish that eat them when swimming.
As for their their resistance to intestinal "travel", I believe that most fish stomach will dilute that little calcium supplement in no time, loll.
A single betta was able to to extinguish any attempt to put them in a food web. and I was seeding heavily.