Doc breaking his own rule makes no sense

Doc is adamant that Marty uses the word 'when' instead of the word 'where', when talking about Einstein's... err.. whenabouts?

However, he then almost immediately reverts to 'where', even when talking about temporal coordinates instead of geographical ones.

When he explains how the time machine's very limited and thus crappy UI works, he says 'this one tells you where you were..'

Wait, shouldn't he have said 'this one tells you WHEN you were'?

The same mistake then occurs when Doc says 'You've gotta come BACK with me!' - not only because he should've said 'FORWARD', not 'BACK' (even if it IS his personal, individualistic past, they can't GO there, so they can't go BACK to Doc's past by going to both of their(s?) future!)..

..but also, because Marty asks 'Where?'.

This is the second time Marty has confused 'when' and 'where', and although Doc correctly rectified this the FIRST time, somehow he doesn't maintain this, and simply starts talking about the 'future'.

Wait a second - why would he NOT correct him here, but he corrects him earlier? Shouldn't Doc's response have been 'You mean 'When', Marty, not 'Where'!'?

Of course it's partially Doc's own fault for even talking about the future as if it's a location instead of .. err, I am not sure if there's an equivalent word for 'time', but still. If you are going to correct someone for using locational language when referring to time travel, you should at least be consistend and conguent with it and correct them EVERY TIME.

Things happening as the movie shows us makes no sense.