I don't recall seeing anything about pustules on buds. Unless that happens I wouldn't think the deadheaded flowers are any more of a risk than anything else in the environment. Spores must end up on the ground anyway when they release from the leaves or wash off in the rain. Except for spores that get splashed back up onto green leaves and then get a chance to germinate, they'll eventually die. So I wouldn't be concerned about it, personally.
