Hardware register default value doesn't make sense on DMG for CGB-only registers

In the Power Up Sequence page, at the bottom is the hardware register table.

For example for the HDMA registers, it doesn't make sense that they read as $FF on DMG, as every register that doesn't exist reads as $FF, so it's slightly misleading. Technically correct, but nonsense.

It would be better if these registers would get flagged as `--` or `N/A` or something similar, perhaps with a clarification at the end of the table that all undefined registers read as $FF.

If `N/A` in capital letters is chosen, it's difficult with vision problems to differentiate at a first glance from just a regular hexadecimal value in nearby cells, as it has the same height, and almost the same width, very much blending in with the other nearby cells.
Adding a footnote link (the superscripted tiny number to the right of the cell contents) should be a good step to make it slightly easier to differentiate if no non-intrusive differentation method is available.