Um...part of it is probably because of that yes due to what I stated previously. Customer is given the suggestion to look at the XB1. It's in stock, has some added features, and you can get the same games. Having worked retail for many years in the past I don't think it'd be all that difficult to sell someone on the XB1 if they were looking all over for a PS4 and had no luck. Even with the $100 difference.
I know if I was dead set on a new console for a gift and was eyeing the ps4 and couldn't find it I'd buy the XB1 in that position rather than wait. Especially if the games were available on either platform. It benefits MS in the North American market too.
Having both I can say with confidence that right now it's a wash. I could flip a coin and be happy with either one. The exclusives between them aren't exactly show stoppers IMO(*yet). The multiplatform titles don't have enough differences between consoles to make it a clear decision.
I think that's a tougher thing to do nowadays. 2 generations ago, the PS2 had a pretty-big lead (what, 2 years) over the original Xbox, as far as release date is concerned. Last generation, the Xbox 360 had a year of sales to eat through before the PS3 launched. Now, the fact that they launched a week apart, that can lead to the "settling" purchase.
However, I feel that the brand loyalty has sunk in pretty heavily, given that Microsoft now has more than a decade in the business (and with Xbox LIVE) under its belt. Odd are, the only people you can get to pick the One over the PS4, because the PS4 is not available, are the people who were going to switch from the 360 last generation. At least, that's the majority I'd see "settling" on a One, those who are already fans of the platform, but were going to go PS4 due to price, power, or general displeasure over Microsoft's policies.
But those who were on the PS4 from the start (read: the majority of PS3 owners) aren't likely to switch to the One, and I'd put those people in the <5% of PS3 users area. Folks buying a console for the first time are probably going to be tough to convince if they have any friends or family on a specific platform, meaning the majority of the "new gamer" converts would be those who don't really have anyone to play with on PS4 already.
The majority of folks already made up their platform minds for this first 6 months of sales, I think. But that's just what I think.