depends entirely on what you’re trying to work. If you are working to enhance lactic tolerance, this is helpful for your SE session, and has the benefit of reducing the need for separate SE and lactic tolerance sessions, but if you’re trying to enhance alactic qualities, you’d steer clear of this for that particular session.
That said, the line is a bit blurred and occasional SE sessions like this might shift the line before lactic sets in and help you stay in alactic conditions longer BUT it might also work the other way!
I suspect the former because Marita Koch improved in both 100 and 400 in lock-step till 1983 and might have officially improved her 100 if she’d competed there up to 1985 (she did unofficially lower her 200 to 21.56 in a time trial in 1985). I simply don’t know for sure but perhaps PJ has seen something in the East German literature to suggest a definitive answer.