A theory for why paper filters below the puck are good is that they aid even flow and reduce channels, allowing you to grind finer and in general, boost overall extraction. As with other elements of espresso prep it’s down to how much of a problem you had before and if you can be bothered with the extra steps.
It’s not too much of an inconvenience for me and I find along with a top shower screen it aids cleanup by compressing the puck, but I understand it’s not for everyone especially those who enjoy darker roasts where it’s less effort to get the most out of them. For those interested, make sure the paper filter is not larger than the bottom of the basket and crawling up the sides as I’ve seen some YouTubers do. For ideal evenness it needs to cover the holes of the basket and not substantially more and it needs to be wet, but I’d suspect a roughly fitting dry paper filter would still outperform none in terms of squeezing the most extraction out.
What I found interesting about the new Wafo baskets is that from their testing, they said their basket boosted comparable performance to other precision baskets with a bottom filter. So they’re really offering convenience rather than an improvement on the combo.