Thanks for reporting.
Deflectors don't block spread, they're "bad" tiles that split adjacent similar tiles into separate groups, increasing the challenge of the group-selection mechanic. In the new version, I changed the art of Deflectors to better communicate that.
What'd you change? I was worried about the tile highlights from when you click a spore spire; I know that the creepers aren't blocked by the now-far-worse-than-useless anti-space-cannon-shields for presumably the same reason cars aren't, but the radioactive spore spewers seem like they'd be somewhat more impeded by them.