When disconnecting an attached device, is it necessary to do so via Eject link?

The Eject option is provided just to make sure that data is not corrupted. If you pull out the external drive while some write or read operation is in progress, it can corrupt the data on your drive.
Linux and Mac always show this option for all removable drives. While Windows does not provide Eject option at times. In fact, Linux and Mac have not much precautions set in to avoid data loss. Windows, however, has the ability to avoid it.
Write Cache is one of the reasons you need to be using the eject button. Also the external drive may be in use in the background for a reason that we do not know. In some strange cases, she file may have been locked by the program using it even if it is not in use. Pulling out your drive without ejecting in such situations can result in data loss and corruption of your drive.
Though there are no hard and fast rules that make it compulsory to use Eject option, yet it would be a good habit to cultivate.

For devices released prior to USB 3.1 unfortunately you have to go through that process of removal. The reason being that, the older devices need to send unmount signal to the OS.

This ensures the data integrity and also avoids any potential damage that may cause due to accidental removals.

The reason that practice is being forced is because your device is constantly sending read information to your OS. And for that reason accidental or sudden removal could lead to damage which makes device unreadable.

Think of it as removal of water tap while filling the tank.

USB 3.1 onwards this practice is taken care of on the hardware end. And instead of constant polling the device is only read when the OS specifically sends the signal.

Even for the modern USB devices it is a good practice to go through the old process of removal. It only helps keep the device in better condition.

I can share my experience.

Once my computer got hung up, so no command was responding. I tried to go through the "eject removable disk" process, but it didn't work. So I had to pull it out. But after I restarted the system, the USB ports stopped working. It was all so difficult, and finally we had to take it to a service center. There they asked me whether I pulled the USB without the "eject" process, so it was understood, that thing caused this entire episode. So, its better not to take risks unless, things are too urgent.