Suspected bug in FSRS Weight optimiser

So if filtered decks do not participate in the optimisation of FSRS weights, why does it show me different results then?

Here is my entire collection

Here are my weights.Note that it says that it has used about 122000 reviews to get these weights.
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Now if I put those same cards in filtered decks which makes it neater

the following FSRS weights are calculated
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This time it says it has only used 59000 of my reviews.

So what is the reasoning behind this weird behavior?