The "new" coin photo in the article are the commemorative coins for the new emperor. While they are technically legal and valid coins, they are not for everyday use. The new coins which have been issued from R3 are different ones, and looks like the rest of the article is talking about them.

I'm not sure which coin the author's brother used. AFAICT, I have no problem using the new (ordinary) 500 yen coins.

https://www.mof.go.jp/policy/currency/bill/20210816.html