The log of creation of page on french wikipedia don't show the oldest entries for example https://fr.wikipedia.org/w/index.php?title=Sp%C3%A9cial:Journal&type=create&user=Xavier%20Combelle which is my creations of page show only a few of created page while I'm sure I created pages before
Personally, I don't think it would be a good idea to backfill that log. The log table is huge and always in danger of becoming too large to be efficiently queryable. We reduced that pressure somewhat with T189594, but the table is still large and unwieldy. Adding several million new records for historic page creation events would exacerbate the problem and not deliver a whole lot of user value. Hopefully one day we will shard the log table by year (or some such strategy) and be able to revisit this, but I don't think it would be a good idea right now.