With Tesla changes and uncertainty regarding feature are a constant concern. While unfortunate, this fits a past pattern. Tesla discontinues retrofits whenever it makes sense for them and that might be rather quickly after introduction - same with factory-installed car features. They seem to offer very little in terms of continuity and expectactability for their customers, it is constant change, change, change. And not just for the better as can be seen, but often times also for the worse.
I think the suggestion that this may have happened because it may have affected PuP sales sounds plausible. The PuP certainly has lost a lot of its value due to the removal of ventilated seats, compared to its price that has remained the same. These two events happening at roughly the same time (HEPA filter retrofit, ventilated seat discontinuation) was a double hit on its value, especially when they did not change the price.