First off, there's specifications and then there's the real world! All the specifications are rated outdoors in a farmer's field with no obstructions and not electrical interference. You'll see nothing like that in the real world.
If you have WiFi (who doesn't?), the range can be seriously impacted. WiFi and BT both use the 2.4ghz frequency spectrum. WiFi has the benefit of also having the 5.8ghz frequency to use when you use current devices. Also, just the environment can have a huge effect. For instance, I has to install a mesh network (Google WiFi) with four repeaters just to properly cover my 3,000 sq/ft condo! Yes, there is a lot of WiFi around, however if I run with BT, there will still be a lot of WiFi around. I started out trying to do it with three repeaters, but try as I might, I had dead spots that I had to add another unit to cover.
Now let's discuss the version of WiFi that they chose to install in the locomotives. My guess is that it's not BT5, but rather one of the earlier versions, most likely BT4. BT5 has only been around for a couple of years, and knowing how price sensitive Lionel is to what goes into the trains, I'd be very surprised if they're using BT5.
