Surely all this RL process did was speed up what the computer would have learned, by a large stretch? The "cost" factors they chose would have hit them ultimately, regardless of if the bot stood still in the base, or wandered off elsewhere.
(1) Not creepblocking at all, and letting your opponent have your creeps under their tower
(2) Modest creepblocking to punish (1)
(3) Severe creepblocking to punish (2)
Would be better than some hand-trained RL creepblocking which is divorced from game outcomes.