That’s not what the video says. It says (and quotes the relevant standard) that they’re optional, and used for manufacturing purposes.

Yes, this video is the undeniable truth. Anything this tuber doesn't know isn't real.

The video isn't, but the standard is.

The standard states they are optional, but provides no logic as to why a manufacturer would go to the trouble of punching these holes at great expense that are apparently unnecessary.

Look around at your high power appliances, exactly all of them will have holes in the prongs. There must be a reason don't you think?

Just in case you missed it - high resistance connections particularly harm high power applications where the total power loss at the connection is proportional to the resistance multiplied by the current squared.

When you are operating near the threshold for the maximum allowable current draw on a single circuit (nominally 15A in USA), this additional power loss can make your device or product fail certification.

This feature is called self cleaning contacts. It is a well known technique in the connector world. Which this tuber is not a part of.

The video contains a video showing exactly how the holes are used in manufacturing.

You seem to dislike people who create content on YouTube but this video seems well sourced.

You are missing the point - people can make content on youtube all they want, but that doesn't make it correct.