Depends on the purpose and whether you are talking about the beginning or end of the session.
If you’re thinking of increasing ROM with longer holds, then the most favourable time is the end of the tempo session. It is likely the stretching at the end of the speed session is for restoring existing ROM.
That can be the ROM that was present at the beginning of the session as opposed to that which might be normal overall. The decision on what to go for depends on recovery status, overall workload from the phase, individual session workload, and the intensity of the just completed session.