I wouldn't like to be in the traffic and that video but nor would I like to filter through it like that. It only takes one car to try to switch lanes and I'd be in trouble. As a driver, I doubt I'd expect a cyclist to come up the inside of me from the outside lane of dual carriageway. I shake my head a motorcyclists doing it so why wouldn't I think the same for a cyclist doing it?
Don't think this is much of a riskl, especially in slow traffic (and not a risk at all in stopped traffic). Changing lane requires a knowledge that the next lane over is clear. Drivers do check their mirrors fairly well in such situations, they like their paintwork.
Next, you have a signal, which is a good forewarning of danger.
If a driver forgets both of those, you'll see the car's wheels begin to turn before they start moving significantly across your path.
If there's a gap opening in traffic, there's a reason for it.
Filtering IS relatively high risk but compensating with a high level of alertness can help.
I don't know why you'd shake your head at motorcycles doing the same thing, it's pefectly legal and as long as other road users stick to their own basic obligations of maintaining awareness of what's around them and signalling their intentions, they should not be disadvantaged or endangered in any way?