textEditor.selectDown([rowCount]) extends selection down a specific number of rows instead of lines. When there are wrapped lines, 1 line can span 2 or more rows. This leads to inconsistent selection lengths when there are wrapped lines.
Documentation says “Extends the editor’s primary selected range downward a specific number of lines.” Either code or documentation should be updated to be consistent with whether it’s meant to be rows or lines.
Assuming textEditor.selectUp() is also affected.