Kiev's success in slowing down the Russians is entirely based on their ability to dig in incredibly hard, forcing the Russians to use heavy equipment to blast them out, and using drones to destroy said equipment when it gets concentrated. Abandoning what is effectively modern island hopping for a "elastic defense" when you lack air superiority and heavy equipment to conduct big counter offensives and win meeting engagements is so stupid that I not only doubt the claim, but believe that if Ukraine tries this, they'll revert back to digging in wherever possible. Rzhev and Kursk showed that with time, even flat, open terrain can be turned into a defensive nightmare, and Ukraine's had more than enough time to prepare.