This.There's no precedent for Iceborne (cheaper MH extension available as download) so no one really knows how to interpret it, and whichever "side" you like the number will be spun to be negative/positive.
Retail is nothing impressive of course but it's only a small part of the big picture.
For all we know all of MHW owners could have bought the add-on digitally or only 10 percent of them...we just don't know.
Still a bummer to see that the Era of massive retail software launches is coming to an end...only Nintendo, Pokemon and mainline DQ left.
Last gen 3DS had a couple MH releases starting with +1m resulting in more exciting times for the retail market.