Reserving 5 Mpbs bandwidth for a ~400MB file for an hour long episode?

No. The 932 kbps that you see on the video stream is its average bitrate, across the whole play duration.
The average bitrate cannot tell you how much bandwidth you need to stream the file without buffering pauses. Because video bitrate is usually not constant. It all depends on how much movement and visual detail is in a scene.
You can have a video with a very low bitrate throughout, except for one scene which has frantic motion or e.g. a high amount of grain. The bitrate will go up significantly during that one scene. But in a 1 hour video, a 3 minute scene with a high bitrate will probably not raise the average bitrate significantly, which explains the difference between average bitrate and required bandwidth.
And that one scene will dictate the value of “required bandwidth” to stream the whole video.
And it’s totally possible that the bitrate of that one scene is high enough that even the largest network buffer doesn’t help to reduce the required bandwidth. So the numbers are all identical.

case in point: Tatami Galaxy (2010) has a rather plain drawing style, so the average bitrate is rather low.
But it has an intro which is stylized/filtered real video with constant fast movement and also a credits sequence with rather fast animation with rapid sweeps, zooms etc.
You can clearly make out both the intro and the credits on this graph:


Both intro and credits sequences are up on YT, so you can see what I am talking about.