OK, I've been fooling around and it seems to me the issue arises when there are more than 3 columns are present.
2x5 works fine since there's only 2 columns.
5x2 gets funky after the 3rd column.
It seems to always go 1, 2, 3, then down to the first table in row 2, then back to 4, then row 2 table 2, then back to row 1 if there's a 5th table on that row, etc.
This is true even if there is a "blank" column. For example, I opened 16 tables in a 4x4 config. I then deleted all the 3rd column. TableNavigator behaved the same way. 1, 2, row 2 table 1, row 1 table 3, etc.
Here are some more vids to demonstrate since that's probably confusing:
LINK