I think, feeling (jap. kimochi, chin. qi) is what it's all about when it comes to aikidō.
I.e. aikidō practice - in my understanding - teaches or should teach "to get attuned to ...", to learn to feel, to develop a reliable feeling. And - most interesting - to learn to direct this feeling (kimochi/qi). Within one's own body - and via a contact/atari into the body of the attacker.
And practices such as striking our own limbs and body in warmups and tekubifuri-undo -- are exercises in precisely this development of feeling -- but it is not explained -- nor done mindfully, in most usage (IME).
Striking the body creates mechanical resonance-- and natural internal damping -- both of which have a distinct feeling . Tekubi furi-undo DRIVES a resonance throughout the body -- and can do the same with any OTHER body (fa jin, FWIW). Damping can be actively managed by inverse means. Kokyu tanden ho is the process of learning to feel remote structure through structure in contact -- akin to hearing with your bones -- and ears work because bones actually vibrate, FWIW.