Titans/Megafauna physics and movement speed seem inconsistent throughout the different MonsterVerse installments? They're not:
You see, Titans and smaller Hollow Earth creatures need energy to move that mass around, the physics that affect H.E. creatures only around human size usually behave just like they do for normal animals, even though they're Hollow Earth life forms and not normal animals, but anything from H.E. bigger than a "small" boulder-beetle from Skull Island (watch the 2023 animated show) - including the beetle itself - moves as fast as its energy levels (along with its biology, of course) make it able to...
The Muto couple and Godzilla in 2014, every new Titan from KotM and the classic Toho ones, along with the Big One in S.I. and Kong in that movie, what did all of these seemingly slow Titans have in common?
They were all either just awakened from a long slumber or young Titans, not well experienced with moving their huge weight around, or they had low energy levels!