There are two officially produced variants of Russian bayonets where you will find 6h3 bayonet in the 6h4 scabbard and 6h4 bayonet in the 6h3 scabbard.
It is not mistaken. In the early period of 6h4 bayonets production, some quantity of transitional models were produced. These were classic 6h3 bayonets in the 6h4 scabbard. Among collectors, these bayonets are known as AKM type I transitional model.
A certain amount of Russian bayonets for AKM and AK-74 rifles were made just for export. They were mostly sold (or resold by the third party) to Egypt. They were often identified as “Egyptian bayonets with a red handle”.