You could conceivably do a little tempo after speed work as a cool down I guess. But if you’re trying to get everything in on the same day it’s going to produce some problems. One is that you will have an uneven distribution of work over the week. Even with the reduced CNS demands, doing a full volume of tempo after speed work is a lot to do on one day, and then doing nothing the next day would represent a rather large swing in workload from day to day. Because of that it is also unlikely you would be able to perform the full volume of tempo consistently. Alternating high and low intensity day to day, rather than all on one day and nothing the next, provides a more even distribution and variation of work for the body over time.
A second problem relates to the recovery effects of tempo. If you watch The Jane Project video, Charlie mentions that recovery methods are more effective if you apply them during the upswing of the recovery cycle rather than trying to reduce the downswing. This naturally implies that as a recovery method, tempo will have a greater benefit the next day when the body begins to recover from the previous day’s speed work.
Is that the question you were asking?