No, there is no additional setting and it does not depend on the current file extension or syntax highlighting.
Selecting a line with mouse works as follows:
You can triple click anywhere on a line to select the whole line independent of the configuration option.
If Allow selection of line with mouse in margin is activated (default) then a single click on the small space between left window border and first character of the line selects also the whole line. If this option is not activated, a single click on the small space between left window border and first character of the line only sets the cursor to start of the line without selecting anything.
Independent of the configuration option you can always select multiply lines be clicking on the small space between left window border and first character of the line, hold the mouse button and move the mouse up or down to select the lines. This method can be also used to select only a single line.
As Miklos has written it is not possible to extend the selection when selecting a line with triple click and hold the mouse button on last click.
A double click always selects only the current word or sequence of white-spaces, independent of the configuration option and where the double click is executed. It is possible to extend the selection when holding the mouse button on second click and move the mouse.
If triple click does not select the whole line, check the mouse settings in the Control Panel. Maybe there is a special mouse setting for triple clicks.
Best regards from Austria