Re: Tabs are inconsistent...
"In both cases the 'tab' key gave the number of spaces that was wanted. This is the correct way for all purposes."
Now you are talking about different things. A typewriter had fixed width fonts so a tab would directly relate to a set number of spaces.
In a word processor with kerning and variable width letters the standard tab specifies an exact distance from the margin or page edge, so that you can still align indents etc.
In that case a tab specifying a number of spaces is not the correct way as nothing would line up at all. Therefore it is not the correct way for all purposes.