Is this usage the same in negative sentences?

Question

I want to say "I have not written since December.  Is this the correct way to say that: Je n’écris pas depuis décembre.

Accepted Answer

Hi Jamie, 
Yes indeed, your sentence is correct but it depends what you mean by it .
If you say -
Je n'écris pas depuis décembre 
It means that you haven't been writing since December and it is an ongoing situation.
If you say -
Je n'ai pas écrit depuis décembre 
it implies this might change.

Answer

Doesn't that contradict what's said in the lesson below?https://french.kwiziq.com/revision/grammar/when-to-use-either-le-passe-compose-or-le-present-in-negative-sentences-with-depuis

Answer

I think you're right Alan.  I hadn't seen that lesson.  My sentence does use "ne...pas", which according to the lesson you cited requires Passé Composé.