Why does Jumpman's Randomizer always start on level 12? [closed]

The 1983 platform game Jumpman by Epyx features 30 unique levels. The game gives the player the choice of playing the entire set of levels from beginning to end, or of playing a selection of levels based on their difficulty: "Beginner" mode is for levels 1 to 8, "Intermediate" for 9 to 18, and "Advanced" for 19 to 30. There is also a "Randomizer" mode that allows you to play the levels in random order. According to the documentation:

The Randomizer allows you to play a random selection of all levels, except the first level.

However, in practice the Randomizer works a bit differently. The order of the levels isn't entirely random: at least in the Commodore 64 and Atari versions of the game, the selection always starts with Level 12 ("Robots II"). It's only after this that the levels start playing in random order. Also, contrary to what is suggested by the documentation, Level 1 ("Easy Does It") is indeed included in the random selection. (I suppose the documentation could be read as meaning that the Randomizer plays a random selection of all levels, except for the first selected level, which is always the same.)

I have always wondered about this quirk of the Randomizer. Specifically:

Is the fact that Randomizer always starts on Level 12 a (vaguely documented) bug, a technical limitation, or a deliberate design choice?
If it's a bug or technical limitation, what is the cause?