Mouse "words" vs. keyboard "words"

Hello all,

I noticed something with tk 9.0.1 that I find a little bit confusing.
According to the man pages, in the text widgets, here is the behavior of
some of the bindings related to words:

- In the "Bindings" section, list item 2, it is specified that "Double-
clicking with mouse button 1 selects the word under the mouse";
- In the same section, list item 9, it is specified that "Control-Left and
Control-Right move the insertion cursor by words".

So far so good. Now let's try: in a text widget, I type the text
"foo.bar". If I double-click on "foo" or "bar", it selects the word "foo",
or the word "bar", respectively. Now if I put my insertion point just
after "bar" and press Control+Left, I would expect the insertion point to
move at the beginning of "bar". But that's not what it does: it moves
before "foo", as if the "." was part of the word, when it wasn't with the
double-click. And same the other way: if my insertion point is before
"foo" and I press Control+Right, the insertion point moves after "bar".

I get caught every time I try to move my cursor by words with the
keyboard, and it's kind of annoying. Also, I tested with tk 8.6 and it
wasn't what it was doing, at least on Linux: Control+Left and
Control+Right were identifying words the same way as the double-click
does.

Is the tk 9.0 behavior intentional? If it is, why are words when using the
mouse different from the words when using the keyboard? Is there a
rationale behind that?

Cheers!