This is mostly a confusion about 'r' being a synonym of 'rt', while it's more explicit if we consider 'r' as one default, and 't' as other (as other parts of the documentation do).

Doing `help(open)` we get:

    mode is an optional string that specifies the mode in which the file
    is opened. It defaults to 'r' which means open for reading in text
    mode. 

Later in the same text it's stated:

    The default mode is 'rt' (open for reading text).

Which reflects the wording I want to have, but is confusing that initially it said a different thing.

If we get the html docs, it says "The default mode is 'r' (open for reading text, synonym of 'rt')."
    
Why not just stating that the default mode is 'rt'?