Why were the values of these arrays swapped?

In the old tooltip logic, the tooltip for a composed viewer message, i.e., a message that you had written, would appear on the BOTTOM_RIGHT of the message:

Similarly, in the old logic, the tooltip for a noncomposed or nonviewer message would appear on the LEFT of the message:

However, as can be seen in the videos, this diff flips that logic to match prod. On prod, tooltips for composed viewer message appears on the LEFT of the message:

And noncomposed message appears on the right:

I kept it BOTTOM_RIGHT since I didn't want to break the old tooltip logic and introduce any regressions, but BOTTOM_RIGHT can probably be made RIGHT in the future.