Getting slack time and a long stoppage for loco reversal are two different things altogether.
Slack time is meant to cover up lost time while the other one for what it says. The simple to-the-point logic is that why don't we include that time in its stoppage?
Plus 35-40 is WAYY too much. It barely takes 15-25 to the max (if not 10), provided its not delayed unnecessarily.