Orin chips come with 2 lanes for UFS already (or so I'm led to believe), so they could in theory go with eUFS 3.x and UFS Card 3.0 and each uses its own single lane. It all depends what the price difference is between eUFS 2.x and eUFS 3.x; if it's negligible, then they could do that. It's all about which ends up being the cheaper option, using eUFS 3.x or adding 3rd lane.
The major downside of CFExpress is its price, its size and how different sizes have different max speeds.
Most CFExpress cards on the market now are Type B (because that's what the cameras and video recorders use), while the smallest is Type A, but even the smallest size is twice the size of a microSD card, nearly 3 times the thickness and has a max speed of 1000MB/s, under the speed available to UFS Card 3.0. Type B is 2000MB/s, but it requires an additional PCIe lane to get there and is also 4 times the thickness of microSD and larger than a standard (as in non-micro) SD card.
And as for price, the cheapest I found was 128GB Type B for $100 on Amazon. Meanwhile, Samsung was selling a 256GB UFS Card 1 for $60.
You're not wrong about CFExpress having a similar ease of implementation, but it's other downsizes (bulkier and more expensive cards) make it the less than ideal choice, IMO.
I'd still say UFS cards are the better choice, but I wouldn't completely rule out CFexpress. The Type A is bigger than a microSD or UFS card (everything is), but it's smaller than a standard SD card, and actually about 20% smaller than a Switch game card, so hardly too big for a device like the Switch. I'm not too concerned with performance past 800MB/s or so, because I don't expect much more from internal storage, with commonly available UFS 2.1 at around 800MB/s being about as high as I expect on that front. That said, unless they roll back Drake's PCIe support to 3.0 (which would be a bizarre decision), it would be compatible with the inevitable PCIe 4.0 CFexpress cards, which would be a 2000GB/s link speed for Type A (probably 1.6/1.7GB/s real world).
And, although CFexpress cards are absurdly expensive at the moment, I'm actually not particularly concerned at how much they would cost were they actually widely used in a mass-market consumer device. Currently the only users of CFexpress cards are either professional photographers or videographers, or they're amateurs who are willing to spend thousands of dollars/euros/pounds on a camera, and as much again on lenses. That is, they're not exactly a price-conscious audience. However, the underlying technology is literally just a NVMe BGA SSD wrapped in plastic, I would assume in most cases using exactly the same chips as M2 2230 SSDs, but with fewer lanes connected and none of the SATA/USB/etc pins that M2 connectors have. In fact,
you can literally put an M2 2230 SSD in a CFexpress housing if you want.
This is why I brought up the Xbox Series X/S expansion card, which is just a slightly modified CFexpress Type B card, but targeted at a much more price-conscious audience. The 1TB card at $220 is about half the price of equivalent CFexpress cards, despite using a more expensive PCIe 4.0 SSD. That $220 almost certainly includes a very healthy profit margin too, as it's a proprietary accessory, so there's no reason mass-market CFexpress cards targeting a similarly price-conscious audience couldn't offer 1TB cards at a sub-$200 price point, which wouldn't be far off the price 1TB microSD cards go for at the moment.
I'd be more concerned about power consumption. With eUFS built for phones and NVMe SSDs built for PCs, the former should have more reliably low power consumption than the latter. Given that UFS cards and CFexpress cards would leverage existing eUFS and NVMe manufacturing respectively, I would therefore expect UFS cards to have lower typical power consumption, and also more consistent power consumption across cards, than CFexpress. The max 1.7W of the CFexpress Type A card I found isn't terrible, but it's higher than you'd probably want for a device like the Switch, and as far as I can see there's nothing stopping other cards pulling 3-4W.