yeah, no. We have no reference for what's happening here, except that they look like shockwaves.
...Then it's a shockwave. You don't need the characters or narrator of a story to [explicitly] describe/explain what's happening in every scene/panel/frame in order for you to be able to identify what's going on. Common sense would allow you to interpret things when you see them especially if they're explicitly drawn or animated. Seconds before we cut to the montage of explosions they made around Earth, Akira and Ryo were trading blows and attacks that had similar effects. The only difference is the coloration of the shockwaves that were made which were [most likely] the animator's attempts to highlight their sides and the themes they were representing. On paper it's still an amazing feat, while contrary to it Saitama doesn't have anything that stacks up to that output wise; nor any durability feats to suggest he can tank it.
Akira got his arms and legs cut off by attacks that are much weaker than a moon kick. Akira can't regenerate body parts without extra help from demons.
The bolts Satan fired at Akira that were shredding his limbs actually peppered the surface of the planet, and the red circles each individual one made when they touched down (indicating the destruction) are actually incinerating a surface area equivalent to that of small countries.
So the attack in itself is still an order of magnitude more powerful than Boros' moon kick (which caps at multi-mountain+) and Akira failing to tank them merely exhibits his lack of piercing durability. Saitama doesn't even have any piercing attacks to exploit that so it's of no matter.
Saitama actually punched an attack that would at least destroy the surface of the Earth. No extra help means one serious punch demolishes Akira's body and unlike Garou or Boros, Akira won't regenerate from it.
The problem with this statement is that you're assuming Saitama could ever tag Akira. Akira's flight speed is fast enough to escape the AOE and range of serious punch, and in close quaters combat Saitama would never blow because Akira has Light Speed reactions for swerving the moon splitter up close. Saitama could probably do some damage if Serious Punch landed, but it never will and a million years, and Akira could legitimately one-shot him with a punch. He has two other striking feats besides the shared one with Satan that overtax Saitama's physical durability.