No, total. For comparison they quote the replay files at what was it, 5GB? It's a classic space-time tradeoff, but in deep learning right now, hard drives are far cheaper than CPUs/GPUs. Playing out the games as you need individual datapoints would probably be at least twice as slow, while anyone can easily store 300GB these days.

I believe the 400GB is the total amount for the 65000 different game replays

I am aware of that. The point remains the same: both Brood War and SC2 are expensive to run, so you really don't want to and it's worth spending disk space to cache the results of playing out a replay files. This will probably also be true of the replay files DM/Blizzard will be releasing even with the lite client.