I would like to see this point disproven, keeping all the 'cross' pieces in the bottom layer makes edge pairing super easy, and if someone could slice turn very well on a 4x4 they could go into their first block knowing exactly where 2 pieces already are, and without having to look in the bottom layer. Sure building the cross may seem like a wasted step, but for how easy it makes edge pairing, and the lesser move count of using roux would negate that. Not to mention having two edf pairs pre orientated would he and the LSE easier. But still, who can slice that well on a 4x4?
I know this isn't as free as normal 3x3 Roux, but what if instead of 3 white pieces on bottom, you put white/blue, blue/red and blue/orange on the bottom so your first block would be completed by orienting the WBO and WBR corners, putting them in place with a R2 and completing the first block with an F and B' move?