Piano Forum

Well obviously there's a difference between playing just octaves and playing presto octaves in the coda of Liszt. One cannot expect to instantly grasp the octave speed just by a single solution as presented by your video as most likely person understands this concept already.
The reason I mention slow practice and building endurance overtime is that having a fast octave speed with efficient movement is difficult to achieve and just simply takes years and years of practice just like any technique where your capabilities extend larger and larger. The octaves in Liszt Sonata is probably one of the pinnacle examples of fast octaves and for him to expect any sort of easy access is simply naive. Slow practice builds a better foundation as most people become less strict in accuracy/tone when practising faster. Once OP can master playing slow octaves with absolute easy with perfect accuracy (without even touching other notes) with good dynamics then they can build from there. If they already have done this then all I can say is just have patience.
A personal example from myself is when I was practising Hungarian Rhapsody no.6 - Liszt and in the first month I could only substain the octaves for the first page in a decent tempo before succumbing to tension. Over the next few months, just by chipping at the octaves, I can substain the octaves for the entirety with less stress.