Yes, it's a new strategy in recent years. To purposely sit out one or both of the first two legs of the TC to focus on taking the Belmont. It's one of the main reasons it's especially hard to win the TC today.
There’s really nothing new about it the strategy. What’s really happened is that the east coast horse owners have no interest in the TC. They’re professionals, horses for them are investments, they run them for profit, and they have no need to join the circus that is the Derby, they tend to run at the Peter Pan instead (last weekend). Meanwhile there’s a bunch of west coast owners that THINK they want the TC but are unwilling to do what it takes to properly prepare their horses (no horse has ever won the TC that didn’t previously win at Belmont). They’ve taken over the Derby, making it an over crowded field none of the pros want to race at. And the basically nobody but the Derby winner cares about the Preakness anymore, so they win that one easily. Then lose to the pros at Belmont.