Ok, I just confirmed this in 4.072.
I had advanced logging turned on but it contains no useful information on the spawning, at least I can't see any
I just continued that game and mpw have a save where - after 4 reinforcement waves where I killed all but the spawners - 92 MK2 spawners are bombarding me. Unfortunately I cannot post it because of my bad internet connection, upload times out :/
They still have sniper range and with only 10 spawners my full fleet is still unable to kill all of the blades before they can do damage - 2 to 3 are getting through. They seem to be so fast that they reach their target before the lower range ships can even react.
As long as you can kill off 70% of the blades with a reasonable point defense force, per cap Dps seems ok to me.