Do you consider handstand and it's variations indirect TVA training? I cannot get into a handstand unless I suck and squeeze my midsection as hard as I can, which feels similar to how I contract in stomach vacuums or planks. The two latter exercises are too boring and do not directly lead to any calisthenics skill, so why not recommend handstands for TVA training?
Second question for you guys that mastered the handstand and are doing much harder variations "HSPU, One arm handstand, leaning handstands, HSPU on straight bar etc " Do you still consciously think about squeezing your midsection?