Asked service center about this a few days ago. Said he researched it and the official word is that installing the HEPA filter will not be effective unless the software is also added. Recommended against just installing the filter.
Believe at sometime in the future they will make adding the filter and software available as a package.
I personally disagree with this based on how the car seems to be setup. Of course it’s the word of a bunch of forum members vs the Tesla SC. My SC told me this once, I talked to Parts member and they were happy to sell me the part and I installed it. Personally I think it is working but I have no validation, at any rate it at least can’t hurt.