Maemish,
You just posted 2 things

#1 - You just posted a long rhetorical question that you also answered in the same post.

#2 - You explained the fact that since Linux is based on how the particular functions and structure work, and since Maemo works on the same structure ...
whether or not it is worth understanding it.
It is a moot point you have argued.

If you wish validation or affirmation.

It is obviously not necessary to know....
if one wishes to simply "use" an n900....and simply "use" maemo apps available.
Then, of course, one is limiting oneself...
to only what is able to do within those parameters .

But...if one wants to do more, solve more, figure out more, fix more, etc...

It helps to learn more.

Also...remember it isn't a race or contest ...
It isn't necessary to sit down and learn everything all at once ...pouring over "how to's"
Learning as it is needed for whatever one is working on makes more sense than filling one's brain with stuff not needed until it is needed.