It is considered. The consideration is that they are lumped together rather than uselessly splitting them apart. The total sales are higher by x amount, even taking trying to take into account sales going to owners of other SKUs.
What other considerations are you wanting discussed? You havn't really explained what you think the consideration should be. That the install base of the PS4 is not nearly as big as the hardware 'sales' number would have us expect it to be?
There are PS4s that were bought and have been sold to re-sellers already. Same with Switches. What about consideration for those?
I guess what I'm looking for is if the two are to be compared, we should try to account for as many differences as there are. Of course, some are insurmountable but the existence of different versions of the PS4 versus there being only one version of the Switch is one that may very well be surmounted come the end of the year. Until then, the PS4 has that advantage over the Switch: a Pro can convince someone who already owns a PS4 to buy another PS4 console.
And as said originally, the 3DS and Nintendo mini consoles could potentially lure people away from a Switch purchase.