As other person has pointed out, you are extrapolating retention from population data which is a misuse of the data presented, as we do not know how many accounts are new, how many are on the free trial (which wasnt as extensive as it is now) and how many are returners. We can only analyze the population by numbers and the feedback out of the steam data out of which so far we can see 3 things:
-DT has less average population than EW on the same span of time
-XIV population growth seem to have stopped for the time being
-DT is so far the expansion with the worst reception (this in both steam score and metacritics user score)
If we want to analyze retention we could do some analysis like luckybancho does, tracking based on how many people finish MSQ from patch to patch but we are too early into the xpac to see that kind of analysis and even that one is flawed, hence why I ask for a source, because so far, outside SE exclusive data there doesn't seem any kind of proper analysis from which we can see the retention.
On a side note trying to say that the people who leave silently are insignificant is... naive to say the least. That is a lesson that the devs had to learn when salvaging the disaster the version 1.0 was:
Those silent are the first to leave and many may not come back if changes are not introduced.