They are probably Chinese copies.
The original NAs have a network function through the RJ45 connector, in the Chinese copies there is no presence of this connector.
In some copies there is the presence of the RJ45 connector, but they are not functional, they only serve to deceive the most unsuspecting.
Yes, you can use NA without the network function, but you will not be able to play games online and you will not be able to pass games through the network cable, the only function of these adapters is just to use an internal HD in PS2 Fat.
If you only intend to use it to connect an internal HD to the PS2, I believe it will meet your expectations.
However, Chinese adapters have very low quality parts and are notorious for not being very durable. Some people cite the Gamesstar brand as being the best among these adapters, with many positive reviews on sites like Aliexpress and Shopee, but be careful when buying one of this brand as it is a clone of the original, and some companies produce the Gamesstar clone with quality even worse, producing a clone of the clone if you know what I mean
Besides, original NAs only support IDE HDs, being possible to use SATA HDs using a BitFunx adapter.
Gamestar adapter:
BitFunx IDE > SATA installation
comparative NA original and gamestar (Use BitFunx parts?)