Mark, I absolutely agree that deliberately named buttons are clear and unambiguous. I agree also that usability is much more important than maintaining an impracticable (or worse) consistency. Look at Windows, proves this point abundantly at times. (And yes, I am somewhat overwhelmed by the complexity of the code and not deeply looking at it.. been away from any coding for over 10 years and never learned php, but I am persisting.)
Consider this, we have a black box in a file picker. The file picker is used for two different purposes, one is to select images and offer the user the opportunity to either upload and store or upload and use the image. The second purpose is to provide a course's writer the opportunity to create links to local or external files. When we look at these purposes they are actually very much identical, it is really only the end use that varies. (To complicate this we have two file pickers, one is a simple html form and the other is - I donno - complicated.) Do I care how the file picker does this? No, I don't. It can be darkest voodoo magic or just a little old lady running at lightspeed to make the connections with unbreakable fishing line then dragging the files back. It is a black box. Who cares what goes on inside - not me!
Look at each of these things, they both have the same basic features, a title bar, a set of tabs, and two buttons at the bottom, Insert/Update and Cancel. The tabs are different and they have different elements on them - but I am not interested in the tabs, they are specific items. They are both almost identical on their first tab - the one you get when you open the form. The image picker uses a "button" that looks like a title or a bit of text. The link picker uses a smaller browse button off to the right end of the uppermost textinput box. Neither are really obvious, but the small browse button is more "intuitive" because it looks like a button.
What Mauno proposes, adding that same button in the same position the image picker is sensible and would probably not require too much work - delete one bit and include another on the same tab. May even be better than adding a third button below. Beginners are not going to want to get too involved in much past the first tab initially, the additional functionality is for later exploration. And that is where the whole thing comes unstuck for me. Without that same approach, across those two forms, it can confuse the beginner. And that is the person to whom all visual elements should be aimed. Who cares about the expert? They know what they are doing, it is the tryro that needs be catered for - and I think that may have been forgotten with some aspects of Moodle 2.0 - but that is another agument altogether. Anyway, if the beginner can look at something and work out what it is they are looking at, then that is an element that achieves a state of "intuitiveness".
Sorry about the length, but I hope I am making it clear now. Just the text "button" on the image file picker, ugly, and inconsistent with the browse button on the link file picker. So replace the text button with a browse button located in the same place as it is on the link file picker, so they both use the same process to go look for a file. Or, replace the little browse button with an ugly text button in the same place that says, "Select/Create a link" or similar.