Don Hodges confirmed this was a rumor a few years ago (I asked him to look into it):
· Grid Bug stage: "Sometimes a Solar Sailor will appear at the start, sailing across the top of the screen. It will drop a "bit", which is worth 5,000 bonus points if you can grab it! There's a 50% chance of it appearing, but only on certain levels, and some levels can never deploy a bit prize. The check whether or not to deploy the bit prize has 3 steps. First, it checks what I call the difficulty. This is dependent on the game level and on the actual difficulty setting which is set in the service mode. If this value is less than 9, a bit will never be deployed. Next, it checks a value from a table based on which pattern of grid bugs is being played. There are 9 patterns. Of the 9, only 3 have a value which will allow for the bit prize to appear. If the pattern is not correct, a bit will never be deployed. Finally, the game generates a random number and looks at one of the bits. If it is clear (50% chance), it does not deploy the bit prize. If it is set (50% chance), a bit prize is deployed. The random number is generated from the Z80 R register, which is an excellent way to generate an extremely random number. It's the same register that is used for random fruit prizes in Ms. Pac-Man past the banana level. The test for the bit prize is called every time the grid bugs screen is started. So, if a player dies on the grid bug screen, this test is called again and could deploy a bit, or not, depending on the factors listed above."