I like training Taiji with fast speed. It makes me feel young. Who said that old people have to move slow. It's nice to see some effective kick/punch in Taiji solo form training.
From my reading of his Taiji, Wu Tunan started in Wu-style, but developed something softer, more internal, deeply focused on emptiness, intention, and qi. It’s called Wu Taiji, but it’s very much his own.
He was known for his age, and for what some might call high-level internal skill.