Piancavallo is connected to absolutely nothing except to some extent
La Crosetta (~12k of flat), which is in Veneto and therefore off limits for an all-Friulian final mountain stage. So the penultimate climb will be >50k from the finish, which means you almost completely eliminate the potential for action before the MTF on your final mountain stage, which in turn means that a gap of even 1 minute becomes almost impossible to overturn unless the GC leader has an offday. The Covatilla MTF on the penultimate day of the 2020 Vuelta is a great example - Roglic was on a bad day, but because there were no climbs anywhere near the MTF, Carapaz couldn't attack from range, and because the MTF itself also wasn't that hard (and Movistar helped Roglic) he could only claw back 21 of the 45 seconds he needed. That could have been one of the most memorable days of the season given the GC situation, but the route ensured it was a bit of a damp squib. Bola del Mundo in the 2012 Vuelta is also a good example of a high-potential GC situation ruined by the stage design.
Zoncolan and Lussari are so hard that they are likely to block any action before the MTF on both the stage itself (if it's a road stage) and on the stages before it. While the 2023 Tre Cime stage being raced abysmally defensively cannot be solely blamed on the Lussari TT coming the day after, it was definitely a factor, and the end of the 2014 Giro was also not exactly a classic.