What he means is making the front chainring variable in size, so it can be the equivalent of a 32T, 33T, 34T, 52T, etc depending on the position of the front shifter.
Theoretically it's possible if you work with a lot of small segments that all expand outward. The key then is to keep the chainring as round as possible to avoid an exaggerated "Biopace-effect"
That would be hard to do as you are using a chain so have discrete steps. 'expanding' means it's not discrete steps (or digital as they like to all it).
A belt would probably be able to do it, but only if a toothed belt where not used.
Only possible solution is to have the teeth suddenly pop to their desired radius as soon as it leave the chain and at some point insert the missing tooth, sounds a bit complicated and unfeasible to me.
What is shown here is basically the Browning system take a step further.
I think it's rather neat.