That's almost but not quite correct. The idea that the "just cut out the middleman" is wrong. They cut out a lot more than that.
Bikes direct basically assembles bikes based on whatever they can scrape for cheap off of the market. They admit as much since it's their business model. So you will never be sure exactly what parts you will get because it's basically spec'd as "whatever frame turned out to be a bad seller" or "whatever random headset can be acquired the cheapest". This could very well mean you are getting parts that are faulty, counterfeit, or failed qc. Or maybe it was just a production overrun and it's perfectly fine. You won't really know.
Bikes direct bikes are sort of a mystery box. Yeah, they are 25% cheaper or something, but you are basically buying a wildcard, so it's not a fair comparison. Usually it ends up being a franken-bike that's a mismash of different standards, odd size or geometry, and hard to upgrade. On top of that the bikes are "assembled" as quickly and carelessly as possible so you might as well be getting a frame and a box of parts because if you don't have a death wish you will need to check every bolt and bearing. My BD fatbike came with cranks that were binding and needed a spacer. And the headset was clunking and I found out they didn't even scrape the paint off the frame where the headset fits and the head tube couldn't be reamed so I had to loctite in the new headset. And the seatpost is a bizarre size I didn't even know existed, so I can't put a dropper post on it. The tires were horrible and had to be changed. On the plus side it was impossible to buy anything else at the time during the supply crunch, and everything else was hyper inflated, so BD was a good desperation option. At the time people were buying BD bikes to strip the parts and throwing the frames in the trash. But the cost is low and the value is also low.
I would still say a random BD bike is probably better than a random Walmart bike. But a random Walmart bike will be cheaper. A random BD bike is NOT, however, better than the best Walmart bikes, and not better than Walmart bikes at the same price tier. There are actually some decent bikes at Walmart, especially Pacific Cycles brands. The Mongoose Dolomite, Grit, and other bikes are actually really good and lots of people buy them just for the frames because it's true, almost all frames at a certain tier are made in the same factory. But there is also a lower tier which is the Walmart Bike Shaped Object tier that's obvious because the designs are obscene and the welds look like my ten year old made them (and they probably were made by a ten year old somewhere in Asia). The bikes made by Pacific really are basically the same as the big brands with different stickers. They are usually lower spec but lower spec isn't always bad and nowadays that the parts companies started changing things for marketing reasons, lower spec often means "older spec" which was the standard spec for decades and still is fine.
The Pacific -made Walmart bikes are probably the best value available. I would honestly avoid BD for the most part. It's false economy because it's just as likely to need work or have problems as a used bike, and you don't get the benefit of buying a new bike that's reasonably specd out with modern standards and non-counterfiet (probably) parts and warranty, assembled by a shop with free tune ups, etc. If you are cheap an/or can work on your own stuff and want a project it's better to find something used and fix it up instead. As always, used is the best. Bikes don't really wear out.
